The Banū Mūsā

The BanÅ« MÅ«sā, Muḥammad, Aḥmad, and al-Ḥasan, were the sons of MÅ«sā b. Shākir, an astronomer and companion of the caliph al-MaʾmÅ«n, during the latter’s time as governor of Khurāsān. Before dying, MÅ«sā b. Shākir entrusted his sons to the caliph al-MaʾmÅ«n, who ensured they received a quality education in Baghdad. The three brothers quickly became close associates of al-MaʾmÅ«n and, following his death, were welcomed into the courtly circles of his successors. They were influent politicians and scholars, actively involved with caliphal undertakings and public works.²⁶ As already mentioned, they also fostered scientific research in Baghdad by extending their patronage to other scholars and sending missions to Byzantium to acquire foreign books, which were brought to Baghdad for preservation and translating. Consequently, significant scientific works were translated into Arabic — many of which only survive in their Arabic versions, as the originals have been lost. A prime example of this is the eighth book of Pappus’s Collectio, which was translated into Arabic as Madkhal BabÅ«s fÄ« l-ḥiyal ka-jarr al-athqāl (Pappus’s Introduction to Mechanical Devices for Lifting Weights) by an anonymous member of the scholarly group led by the BanÅ« MÅ«sā.²⁷ But this circle was not only devoted to translation. Several scholars, including the brothers themselves, were distinguished experts in various fields. The BanÅ« MÅ«sā are credited with approximately twenty original works on mathematics, astronomy, music, war engines, and mechanics.²⁸ Sadly, only a few of their works have survived, two of which are dedicated to mechanical devices: Al-Āla allatÄ« tuzammir bi-nafsihā (The Instrument Which Plays by Itself), focusing on an automatically operated organ, and Kitāb al-Ḥiyal (Book of Ingenious Devices), an illustrated work describing nearly a hundred devices. Both texts detail contraptions that function based on a combination of aerostatic and hydrostatic pressure principles, which points to the assimilation of the Greek tradition in pneumatics and mechanics. Primary sources also reveal that the BanÅ« MÅ«sā were attributed with other works related to engines and mechanics. Ibn al-NadÄ«m and al-QiftÄ« mention a Kitāb al-Qarasá¹­Å«n (Book on Steelyard), thus connecting them with other contemporary scholars dedicated to the study of this discipline. Among these figures, we recall the eminent MuÊ¿tazilÄ« theologian MuÊ¿ammar al-SulamÄ« (d. ca 215/830-1), who, according to Ibn al-NadÄ«m, composed a treatise on the steelyard entitled Kitāb Ê¿Illat al-qaraá¹£tÅ«n wa al-mirʾāt (On the Principle of the Steelyard and the Mirror). Other notable individuals include the BanÅ« MÅ«sā’s rival, Sanad b. Ê¿AlÄ«, and their protégé Thābit b. Qurra.²⁹ Furthermore, the Ottoman literati Kâtip Çelebi (d. 1067/1657) credited the BanÅ« MÅ«sā with a work on war engines in his Kashf al-ẓunÅ«n Ê¿an asāmÄ« al-kutub wa-l-funÅ«n (Opinion’s Scrutiny of the Names of Books and the Sciences).³⁰ However, no further information is available about the existence of this text.

The brief text known as Al-Āla allatÄ« tuzammir bi-nafsihā survived in a single manuscript from the sixth/twelfth century.³¹ The authorship of the treatise remains uncertain as it only bears the name of the BanÅ« MÅ«sā.³² Primary sources also provide limited assistance in this matter. While collectively attributing an interest in musical knowledge to the three brothers, they refrain from specifically associating any individual work with them on this subject. ³³

The text introduces a musical instrument (āla) capable of playing various melodies autonomously, ranging from slow rhythms (Ä«qāʿ thaqÄ«l) to quick ones (Ä«qāʿ khafÄ«f).³⁴ The described device is an automatic hydraulic organ that activates a flute player, enabling it to produce a diverse repertoire of songs. Its mechanism operates by utilising subtle changes in air and water pressure and incorporates conical valves as automatic regulators. The device can be described as follows: It involves a large rotating drum with pins that manipulate the holes of a flute through small levers. To create the necessary airflow for the flute, water fills a reservoir, forcing the air to escape. Meanwhile, a water wheel drives the drum’s rotation. The device’s melodic instructions come from a cylinder equipped with teeth arranged to meet the melody’s requirements, similar to the setup of a modern barrel organ. These teeth come into contact with levers that control keys, which, in turn, open or close the holes in the organ pipe. This organ does not have multiple pipes like a traditional one, but it employs a single pipe with multiple holes, much like those found in flutes or reed pipes. The entire machine, standing approximately 150 cm tall, can be concealed within the body of a humanoid figurine, as stated by its creators. Additionally, the text suggests that with a few modifications, the mechanism can be adapted to create a lute (Ê¿Å«d) or psalter player (miÊ¿zaf), which could even be accompanied by figures of images that dance following the music.³⁵ This device is not an isolated invention; instead, it finds its roots in Greek examples of automatic flutists, including those designed by Hero of Alexandria, Archimedes, MÅ«risá¹­us, and Apollonius, whose works were studied and translated into Arabic.³⁶

The musical device was designed to function autonomously, mimicking the movements and actions of a flute player. While there is no explicit mention of its actual construction and practical application, it is plausible that the automaton was intended for display in courtly society.³⁷ Indeed, the potential to conceal the device within a flute, lute, or psaltery player, as well as the possibility of incorporating dancing figures, strongly suggests that it was meant to be part of various courtly events. If it had been built, it would have likely captivated audiences at official gatherings and celebrations, astonishing both courtiers and foreign dignitaries alike. This is further supported by the text itself, which explains that it is possible to control the water flow during the switch between melodies. To the audience, it would have seemed as if someone had instructed the statue to change from one tune to another, with the statue dutifully complying. Alternatively, it could have appeared as though someone had commanded the statue to play a specific melody, and the statue would do just that.

Kitāb al-Ḥiyal, the BanÅ« MÅ«sā’s best-known work, bears no trace of musical automata, except for a few devices able to emit different kinds of sounds.³⁸ The treatise, which appears to be primarily the work of Aḥmad, provides an overview of the operating system for trick vessels used to dispense liquids, lamps, alternating fountains, and some practical tools. A significant portion of the devices detailed in the text comprises trick vessels, with the majority specifically designed for drinking sessions and banquets. For example, some devices allow the cupbearer to dispense liquids as much or as little as he desires; others dazzled the audience by convincing them that a mixture of wine and water, poured together from the jar in front of them, was separated inside the vessel; and others allow the devices to pour water and wine from the same spout and later discharge a known quantity of water from a tap, followed by the same quantity of wine. Such devices indeed were highly sought after at court. Their practical purpose was to generate a playful moment during parties, by delighting, puzzling, and arousing wonder in the audience.³⁹

The primary objective of Kitāb al-Ḥiyal was to showcase the variety of machines created, rather than delving into the fundamental principles of pneumatics, hydrostatics, and mechanics. The BanÅ« MÅ«sā were well acquainted with mathematical and scientific principles, as evidenced by their extensive list of authored and commissioned works. Ahmad’s approach to presenting the content, lacking any theoretical aspirations, was a deliberate choice, not a result of insufficient knowledge. His main objective was to provide detailed descriptions of the machines he designed, irrespective of whether they were constructed by him personally or by an artisan under his supervision.⁴⁰

Recently, Constantin Canavas put forth the idea that the BanÅ« MÅ«sā’s inventions might have been mere thought experiments or performative actions, rather than actual creations of automata, due to the lack of additional evidence supporting their presence.⁴¹ While not all devices presented in Kitāb al-Ḥiyal may have been brought to life, there is other evidence supporting the existence of automata similar to those described by the BanÅ« MÅ«sā in different contexts. For example, the presence of a drinking vessel suitable for parties is mentioned in the writings of al-MutanabbÄ« (d. 354/965).⁴² The poet dedicated a few short poems to a game introduced during a feast by his patron, Badr b. Ê¿Ammār al-KharshānÄ« (d. 330/942), the governor of Tiberias, Syria. The game involved a clockwork toy shaped like a dancer that spun around with one leg raised, stopping in front of a guest who would then drink a cup of wine and improvise verses. Although this model differs from those depicted by Kitāb al-Ḥiyal, this fact suggests that the BanÅ« MÅ«sā’s descriptions of automata were more than just theoretical ideas and that such devices were indeed created and enjoyed in a courtly environment. Additionally, one of the BanÅ« MÅ«sā’s major patrons, Caliph al-Mutawakkil (r. 232–247/847–861), was known to be an enthusiast of mechanical devices, suggesting that the brothers were likely the main creators — or responsible for commissioning — these machines.

The BanÅ« MÅ«sā’s contributions to mechanical technology secured their prominence in the field and garnered them widespread recognition and acclaim. This, in turn, led to their inclusion in all major Arabic biographical dictionaries focused on scientists and intellectuals, starting with Ibn al-NadÄ«m.⁴³ Their reputation endured for centuries, as evidenced by the historian Ibn KhaldÅ«n (d. 808/1406), praising their treatise in his Muqaddima (Introduction).⁴⁴ Additionally, al-JazarÄ« acknowledged them as his esteemed predecessors in his discussion of perpetual flutes and shape-shifting fountains.⁴⁵

The widespread recognition and acclaim brought the BanÅ« MÅ«sā the patronage and continued support of the Abbasid caliphs. They likely commissioned the creation of awe-inspiring automata to enhance the splendour of their courtly settings. Historical accounts, such as those concerning al-Mutawakkil, reveal a keen interest in automata, evidenced by a limited yet diverse collection of Arabic sources.⁴⁶ Within the courtly environments, examples of mechanical contrivances were housed, possibly crafted by the BanÅ« MÅ«sā themselves, their collaborators, or other anonymous artisans. These were artificial trees displaying birds that chirped on their branches, along with animated statues of horsemen and knights. The BanÅ« MÅ«sā’s technical treatises do not mention these particular types of devices. However, the concept of an artificial tree featuring singing birds was a widely recognised Hellenistic invention.⁴⁷

Despite their achievements and reputation, the BanÅ« MÅ«sā were not without controversy. They were known to scheme against their rivals, including those with distinguished reputations in the field of engineering.⁴⁸ Various sources recount their actions against the Jewish mathematician, astronomer, and engineer Sanad b. Ê¿AlÄ«, aiming to remove him from the court of Baghdad and diminish his favour with al-Mutawakkil.⁴⁹ They employed similar tactics against the philosopher al-KindÄ«, as he had reportedly upset them by being chosen as the tutor for al-MuÊ¿taá¹£im’s grandson Aḥmad, who would later become caliph al-MustaÊ¿Ä«n (r. 248–52/862–6), instead of themselves.⁵⁰ The BanÅ« MÅ«sā effectively discredited him in al-Mutawakkil’s eyes, which led to him being beaten and temporary robbed of his library. This valuable collection eventually came into the possession of the BanÅ« MÅ«sā, who, according to sources, managed to do so due to al-Mutawakkil’s passion for automata.⁵¹ Ironically, the brothers Muḥammad and Aḥmad later faced a life-threatening situation during a canal excavation project ordered by al-Mutawakkil. Their rival, Sanad b. Ê¿AlÄ«, whom the BanÅ« MÅ«sā had managed to distance from al-Mutawakkil’s favour, was specifically summoned by the caliph to evaluate their work. Sanad b. Ê¿AlÄ« intervened, protecting the brothers from humiliation, on the condition that they agreed to return al-Kindī’s books to their rightful owner.

Thābit b. Qurra

Thābit b. Qurra (d. 288/901) was a renowned Sabian scholar from Ḥarrān, a city in Northern Mesopotamia known for its tradition of instrument-making, focusing on astrolabes and balances. Initially working as a money changer, Thābit caught the attention of Muḥammad b. MÅ«sā due to his remarkable linguistic proficiency in Syriac, Arabic, and Greek. This encounter occurred while the latter was returning from a mission to Byzantine territory, where he had been searching for manuscripts. Consequently, Muḥammad invited Thābit to accompany him to Baghdad. According to Ibn al-NadÄ«m and later biographers, upon their arrival in Baghdad, Muḥammad not only provided Thābit with accommodation in his own home but also assumed responsibility for guiding his scholarly journey and fostering his scientific education, a scope that encompassed the realm of mechanics. Thābit’s example underscores the significance of educational interactions and teaching activities transpiring in Baghdad during that period, thus highlighting the vital role they played in the transmission and dissemination of mechanical knowledge. Thābit was an active member of the BanÅ« MÅ«sā’s scientific circle, and also tutored the sons of Muḥammad.⁵² He lately succeeded the BanÅ« MÅ«sā as head of their scientific circle and himself founded a veritable scholarly dynasty, including his son Sinān b. Thābit, a physician devoted to astronomy and mechanics, and his grandson IbrāhÄ«m b. Sinān, a mathematician and astronomer. Muḥammad also played a crucial role in introducing Thābit to al-MuÊ¿taḍid’s (r. 279–289/892–902) court and the circle of scholars associated with it. In this milieu, Thābit quickly affirmed his position, assuming the role of an astrologer, physician, and boon companion.

Thābit’s scholarly contributions encompassed both the translation of Greek works and original research. As a translator, he was responsible for the Arabic rendition of numerous texts, such as Archimedes’ The Sphere and the Cylinder, which allowed the BanÅ« MÅ«sā to pursue their work on infinitesimal geometry. Additionally, he also supervised other scholars’ translation activities, as demonstrated in the case of Euclid’s Elements and Ptolemy’s Almagest.⁵³

As a scholar, Thābit’s contributions spanned various fields, including mathematics, astronomy, astrology, meteorology, natural philosophy, and medicine, earning him widespread recognition.⁵⁴ Of note for this study are his several treatises devoted to mechanics, an area seemingly inspired by the research conducted under the BanÅ« MÅ«sā’s patronage. Three studies on the steelyard are ascribed to him, FÄ« l-qarasá¹­Å«n (On the Steelyard), Kitāb al-Qarasá¹­Å«n (Book on Steelyard), and Liber karastonis (Book of the Steelyard).⁵⁵ The latter is a revised version made by Thābit of Kitāb al-Qarasá¹­Å«n, which was later translated into Latin by the Italian scholar Gerard of Cremona (d. 1187) in the twelfth century.⁵⁶ On a related topic is Kitāb fÄ« á¹£ifat al-wazn (Book on the Description of Weight), devoted to the equal-armed balance. The survival of this text is solely dependent on its reproduction in al-Khāzinī’s Kitāb MÄ«zān al-ḥikma (The Book of the Balance of Wisdom).⁵⁷ Thābit’s interest in the subject becomes even more understandable when viewed in the light of his teaching relationships and scientific collaborations which tightly bound him to the intellectual milieu of the BanÅ« MÅ«sā. But his intellectual pursuits extended beyond these circles. Notably, he engaged in correspondence with Sanad b. Ê¿AlÄ«, who al-KhāzinÄ« credited with the development of hydrostatic balances.⁵⁸ This exchange of ideas and knowledge between Thābit, the BanÅ« MÅ«sā, and Sanad b. Ê¿AlÄ« further illuminates Thābit’s exploration of mechanics and related disciplines, solidifying his legacy in the field.

Arabic biographies such as the ones by Ibn al-Qifá¹­Ä« and Ibn AbÄ« Uá¹£aybiÊ¿a also mention two other treatises on mechanical devices, that is Ashkāl lahu fÄ« l-ḥiyal (Designs for Automata) and Kitāb fÄ« ālat al-zamr (On the Organ/Musical Pipe).⁵⁹ As of now, no extant manuscripts of these texts have come to my attention. However, it is worth noting the close relationship between both texts and the scientific production of the BanÅ« MÅ«sā. Ibn al-Qifṭī’s list of works relies on the authority of Hilāl b. Muḥassin b. IbrāhÄ«m al-Ṣābīʾ (d. 448/1055), Thābit’s great-great-grandson.⁶⁰ The reliance on authoritative sources within Thābit’s lineage, along with their association with the BanÅ« MÅ«sā, lends strong credibility to the idea that Thābit engaged in the composition of similar treatises, despite the absence of these two specific texts. Furthermore, it sheds light on the interest of the BanÅ« MÅ«sā’s circle in the science of mechanical devices, as well as the broader Abbasid scholars’ engagement with this field.

Turning our attention to Kitāb fÄ« ālat al-zamr, it should be noted it is closely associated with Al-Āla allatÄ« tuzammir bi-nafsihā, which the sole extant sixth/ twelfth-century copy ascribes to the BanÅ« MÅ«sā.⁶¹ As highlighted earlier, the major Arabic biographies remain silent on any link between this work and the three brothers. The BanÅ« MÅ«sā, more broadly, are not strongly associated with musical studies. In contrast, Thābit’s association with a pipe work is undeniable, underscoring his clear interest in musical studies. This is further substantiated by his authorship of several treatises on music theory and harmonic, such as Maqāla fÄ« l-mÅ«sÄ«qā (Discourse about Music).⁶² In this context, within the list of books composed about motions (al-kutub al-muʾallafa fi l-ḥarakāt) provided by Ibn al-NadÄ«m, several anonymous works can be found that parallel Thābit’s attributed work. These titles include Kitāb Ālat al-zamr al-bÅ«qÄ« (The Trumpet Instrument), Kitāb Ālat al-zamr al-rÄ«hÄ« (The Wind Flute), Kitāb al-Urghanin (The Organ), immediately followed by the BanÅ« MÅ«sā’s Kitāb al-Ḥiyal.⁶³ The omission of the BanÅ« MÅ«sā’s authorship by Ibn al-NadÄ«m in this listing is indeed peculiar. Plausible scenarios emerge: Thābit may have composed a treatise on a musical automaton like the BanÅ« MÅ«sā themselves, in the wake of the interest in this discipline within their milieu. Alternatively, it is conceivable that Thābit authored Al-Āla allatÄ« tuzammir bi-nafsihā, while the BanÅ« MÅ«sā undertook a review, and a scribe inadvertently neglected the original author’s name. In any case, this validates the scholarly milieu surrounding the BanÅ« MÅ«sā as prolific in mechanical studies, notably within the domain of ingenious devices.

Al-Kindī and His Scientific Circle

The philosopher AbÅ« YÅ«suf YaÊ¿qÅ«b b. Isḥāq al-KindÄ« (d. ca. 256/870) came from a noble family of the Kinda tribe, which held significant influence in southern Arabia and Iraq during the fifth and sixth centuries. Born in Basra, he became a prominent figure in Baghdad’s intellectual and cultural life under the patronage of al-MaʾmÅ«n and his successors. Besides his contributions to the field of philosophy, al-Kindi is also recognised for his involvement in the translation movement. He played a vital role in sponsoring the translation of ancient philosophical, medical, and mathematical texts.⁶⁴

Although the details of his education are unclear, it is evident that al-KindÄ« was proficient in numerous disciplines including philosophy, medicine, astronomy, mathematics, optics, and occult sciences. His education appeared to follow Neoplatonic philosophical training, and his learning and writing were closely connected to the translation of texts he sponsored, such as those by Aristotle, Plotinus, and Proclus. Ibn al-NadÄ«m attributes approximately 250 works to him; however, only a small portion of these still exists today, and their authorship is occasionally debated.⁶⁵ In addition, al-KindÄ« also gained knowledge in various practical and natural subjects such as perfumery, sword-making, gemmology, zoology, catoptrics, earthquakes, and meteorology. On one hand, these interests demonstrate his ties to Aristotelian natural philosophy, and on the other hand, they highlight the practical concerns of his Abbasid court patrons.⁶⁶

Al-KindÄ« was indeed a prominent scholar at the Abbasid court and served as the tutor for al-MuÊ¿taá¹£im’s grandson Aḥmad, who later rose to the position of Caliph al-MustaÊ¿Ä«n. Several epistles penned by al-KindÄ« were addressed to this prince. Among the possible writings dedicated to him, there is a work related to mechanics, Risāla fÄ« arkān al-ḥiyal (On the Fundaments of Mechanics).⁶⁷ Ibn al-NadÄ«m’s bibliography of al-KindÄ«, later adopted by major bibliographers such as Ibn al-Qifti and Ibn AbÄ« Uá¹£aybiÊ¿a, mentions this text in a chapter devoted to miscellaneous books (al-anwāʿīyāt), featuring works on a variety of subjects such as catoptrics, perfumery, and sword-making.⁶⁸ The contents of this lost work remain unknown; however, its connection to mechanics appears evident from the very title of the piece. The attribution of this text to al-KindÄ« is seemingly accurate. The way Ibn al-NadÄ«m presents the list, in fact, raises the suspicion that it may be based on a pre-existing bibliography, possibly compiled by al-KindÄ« himself or one of his students.⁶⁹

In addition to al-Kindī’s work, the philosopher’s circle also contributed to the field of mechanics by providing the Abbasid court (and possibly the prince Aḥmad, to whom Risāla fī arkān al-ḥiyal may have been dedicated) with an Arabic translation of Hero of Alexandria’s Mechanica. This work examines the theory of the five fundamental powers (lever, wedge, screw, winch, and pulley), discussing the effects of combining these powers to create more potent machines and describing different kinds of devices. The Arabic translation, produced by the Christian polymath Qusṭā b. Lūqā, (d. ca 300/912–3) bears the title Fī rafʿ al-ashyāʾ al-thaqīla (On Lifting Heavy Objects). Interestingly, it seems that while Qusṭā b. Lūqā was translating Hero’s work, the Banū Mūsā commissioned an Arabic rendition of Pappus’ treatise on the same subject.

David Jackson’s studies explore the scientific activities of the two communities guided by al-KindÄ« and the BanÅ« MÅ«sā, focusing on their independently produced Arabic translations of the Greek treatises during the same period.⁷⁰ Interestingly, Pappus’ later work incorporated excerpts from Hero’s Mechanica books II and III, allowing Jackson to perform a comparative analysis. Through careful examination of both parallel Arabic translations and the remnants of the original Greek texts,⁷¹ Jackson successfully established their autonomy. As the translator of Pappus’ text remains anonymous, Jackson sought alternative indicators to potentially identify them. He, therefore, interprets the previously mentioned hostility between the BanÅ« MÅ«sā and al-KindÄ« as the “social indicator for the independence of the two translations.” This accounts for the “apparently complete ignorance of the translator of whichever of the two was the later translation, of the existence of the earlier one.”⁷² It thus appears that the BanÅ« MÅ«sā and al-KindÄ« were competing for scientific recognition and courtly favour, transcending personal aspirations, and shaping their scientific pursuits, even in the field of mechanical studies.

The interest in Hero’s work confirms that al-Kindī’s circle also had a keen focus on studying mechanics. Indeed, we know that Qusṭā b. LÅ«qā, the translator of Hero’s Mechanica, devoted a few treatises on steelyard (qarasá¹­Å«n) and on weights and measures.⁷³ This further helps contextualise the information provided by sources about al-Mutawakkil’s passion for automata as a propulsor for the plundering of al-Kindi’s private library. In this regard, it can be useful to recall that an almost contemporary historian, Aḥmad b. YÅ«suf b. al-Dāya, reports this account in the Kitāb al-Mukāfaʾa wa-ḥusn al-Ê¿uqbā. Ibn al-Dāya possessed firsthand information, as his father YÅ«suf was not only a foster brother to Caliph al-MuÊ¿taá¹£im but also an administrative assistant to IbrāhÄ«m b. al-MahdÄ« (d. 224/839), poet, musician, and Caliph from 201–3/817–9. The strong connections his father maintained with the intellectual circles in Baghdad and Samarra significantly enriched the content of Ibn al-Dāya’s work.⁷⁴ Based on his report, I suggest that gaining access to their rival’s library could have enabled the BanÅ« MÅ«sā to consult new technical works, thereby streamlining their efforts in designing and constructing automata to indulge their caliph’s passion. One wonders if the rivalry between the BanÅ« MÅ«sā and al-Kindī’s associates contributed to the creation and display of devices at court. By presenting self-moving and sound-producing machinery of various types, scholars may have sought to secure the praise and support of their patron caliph, possibly fostering technological research.

Sinān b. Thābit

Son of Thābit b. Qurra, AbÅ« SaÊ¿Ä«d Sinān b. Thābit (d. 331/943) was an astronomer, mathematician, historian, and personal physician of three caliphs, al-Muqtadir (r. 295–320/908–932), al-Qāhir (r. 320–322/932–934), and al-Rāḍī (r. 322–329/934–940).⁷⁵ Born a Sabian of Ḥarrān, he was later requested to convert to Islam by al-Qāhir, but he fled to Khurasan to avoid it. He came back to Baghdad after al-Qāhir’s destitution, and he later decided to convert.⁷⁶ In charge of Baghdad’s hospitals from 304/916–7, al-Muqtadir also appointed him as the supervisor of the medical profession in 319/931, responsible for licensing physicians after a man died due to a medical practitioner’s error. Two of his sons, AbÅ« Isḥāq IbrāhÄ«m b. Sinān and AbÅ« l-Ḥasan Thābit b. Sinān, also distinguished themselves in mathematics and medicine.

Sinān b. Thābit is credited with several writings in various disciplines, including history, geometry, and astronomy.⁷⁷ The recent discovery of a mechanical treatise fragment attributed to him, known as the Arabic Codex Berlin 3306 (folium 132r-v), sheds light on a previously unexplored aspect of his scientific work. This fragment, housed at the Staatsbibliothek in Berlin and studied by Muhammad Abattouy, also emphasises the connection with his father’s interests and provides greater clarity on his intellectual pursuits.⁷⁸ The writing, consisting of one folium, bears the title Multaqatāt kitāb al-tām li-Sinān b. Thābit fÄ« dhikr uṣūl al-khamsa (sic) (Extracts from the Complete Book by Sinān b. Thābit in the Mention of the Principles of the Five [Simple Machines]). The recto page illustrates the theory of simple machines, including the lever, windlass, pulley, wedge, and screw, while the verso presents the descriptions of several mechanical devices. The text thus holds a unique position as one of the rare Arabic compositions dedicated to the theory of simple machines, drawing connections with the writings of pseudo-Aristotle, Hero, and Pappus, which were available in Arabic translations. The descriptions and illustrations of the simple machines closely relate to Book 2 of Hero’s Mechanica, which was made available at the Abbasid court in an Arabic translation by Qusṭā b. LÅ«qā.⁷⁹

To my current understanding, there is no historical record indicating that Sinān b. Thābit authored a work on mechanics nor is there any mention in primary sources of his involvement or curiosity in the field. The text, however, not only identifies the work’s author with Sinān, but it also specifies that it consists of two fragments derived from a longer treatise entitled Al-Kitāb al-tām (The Complete Book). In the light of the title, Abattouy suggested that it should have had an encyclopaedic scope, with mechanics being one of the sections of the exposition concerning mathematical sciences.⁸⁰ As for the identification of Sinān as its author, despite not having any works on mechanics mentioned in his bio-bibliography, the archaic style of the vocabulary and a few other elements attest that the short text may have been written by Sinān in the first half of the fourth/tenth century.⁸¹

Al-Fārābī

Little is known of AbÅ« Naá¹£r Muḥammad b. Muḥammad al-Fārābī’s life. Born in about 256/870 into a family originally from Khurāsān or Transoxania, he first moved to Baghdad in the early fourth/tenth century, then left for Syria and Egypt around 330/942. Having devoted his life to teaching and travel, he died in Damascus in 339/950-1.⁸² There is no information available about al-Fārābī’s youth and education. After moving to Baghdad, he began to engage with different intellectual and theological circles such as the Aristotelian philosopher and translator AbÅ« Bishr Mattā b. YÅ«nus (d. 328/940) and, to a lesser extent, al-KindÄ« and his associates.⁸³

Al-FārābÄ« devoted himself to the study of various disciplines, composing treatises on philosophy, religion, ethics, music, astronomy, and geometry. His contributions hold prominence in the fields of music, logic, cosmology, and metaphysics. Additionally, his curiosity extended to the study of physics, as evidenced by his role as the author of a work that refutes the existence of void through experimental means, Maqāla fÄ« l-khalāʾ (Treatise on the Void).⁸⁴ It is indeed the debate surrounding the existence of continuous and partial void that led to the development of pneumatics, which studies the characteristics of moving air and the effects arising from its interaction with other elements, particularly water and fire. The basic purpose of al-Fārābī’s work is to defend Aristotle’s rejection of the void using arguments and experiments from the Alexandrian scholars working on pneumatics, such as Hero and Philo.⁸⁵ In doing so, al-FārābÄ« demonstrates his familiarity with the contemporary debate on the topic, likely writing the treatise as a response to the discussion between the MuÊ¿tazilite scholars KaÊ¿bÄ« al-BalkhÄ« (d. 319/931) and AbÅ« Bakr al-RazÄ« (d. 313/925 or 323/935).⁸⁶

The text is organised into four sections.⁸⁷ The initial one introduces the problem and outlines the two experiments conducted, highlighting that the opposing party uses them as evidence for the possibility of creating a vacuum. The following parts are dedicated to a dialectical refutation of his opponents’ arguments, and a presentation of the properties of the material and instruments relevant to the experiments. The closing section focuses on the experiments designed to confirm the rejection of the void. The initial experiment involves lowering an inverted vessel onto the surface of a body of water, pressing it down, and then lifting it out to find that no water has entered it. The following experiment is a variation of the first.

The relevance of al-FārābÄ« for the studies of mechanical devices is also due to the fact that he theorised a categorisation of scientific disciplines in his Iḥṣāʾ al-Ê¿ulÅ«m (The Enumeration of the Sciences), where mechanics found its place in relation to mathematics.⁸⁸ The treatise unfolds in five chapters devoted to linguistics, logic, mathematics, physics and metaphysics, fiqh and theology, pointing out the existing hierarchical relationships among the various disciplines. The third section analyses the mathematical sciences (Ê¿ilm al-taʿālÄ«m), organised in seven parts: arithmetic (Ê¿ilm al-Ê¿adad), geometry (Ê¿ilm al-handasa), optics (Ê¿ilm al-manāẓir), astronomy and astrology (Ê¿ilm al-nujÅ«m), music (Ê¿ilm al-mÅ«sÄ«qā), the science of weights (Ê¿ilm al-athqāl), and the science of mechanics (Ê¿ilm al-ḥiyal). Al-Fārābī’s synthesis of mathematical knowledge thus combines the traditional quadrivium (arithmetic, geometry, astronomy, and music), with optics, the science of weights, and the science of ingenious devices:

The science of mechanics (ḥiyal) is the knowledge of the procedure (wajh al-tadbÄ«r) by which one applies (muṭābaqa) all that was proven to exist in the mathematical sciences (taʿālÄ«m) that were mentioned above in statements (qawl) and proofs unto the natural bodies, and (the act of) locating (all that) and establishing it in actuality (bi-l-fiÊ¿l).⁸⁹ The reason for that is that these (mathematical) sciences concern themselves with lines, surfaces, volumes, numbers, and all their subject matter is intelligible on its own in isolation from the natural bodies. When one wants to locate (these ideas that form the subject matter of the mathematical sciences) and willfully exhibit them (by means) of a craft (á¹£unÊ¿a = τέχυη) in the natural bodies that are perceptible to the senses, one needs a force (quwwa) through which he proceeds to establish them in (these bodies) and to apply (these ideas) to (these bodies). For the material and perceptible bodies have special conditions that prohibit them from accepting (the ideas) that were demonstrated by proofs from being located in them as one pleases to do. On the contrary, these natural bodies have to be prepared to accept what one seeks to establish in them, and one has to contrive to remove the obstructions (an yatalaá¹­á¹­af fÄ« izālat al-Ê¿awāʾiq).

The sciences of mechanics are therefore those that supply the knowledge of the methods and the procedures by which one can contrive to find this applicability and to demonstrate it in actuality (bi-l-fiʿl) in the natural bodies that are perceptible to the senses.

Of these mechanical sciences are the many arithmetical ones including the science known to the people of our times as the science of Algebra (al-jabr wa-l-muqābala), for it partakes of arithmetic and geometry.⁹⁰ It also includes the procedures by which one brings forth (istikhrāj) the numbers which ought to be dealt with in accordance with the principles laid down by Euclid in Book X of the Elements, as to their being rational (muná¹­aqa = expressible) or surds (á¹£umm = inexpressible), or in accordance with others that were not mentioned by him in that book. For since the ratio of the rational and the surds to one another is like the ratio of one number to another, then each number is the counterpart (naẓīr) of some magnitude, be it rational or surd. If one could bring forth these numbers that are the counterparts of the ratios of these magnitudes, then these magnitudes would have been brought forth in one way or another. For that reason, some numbers are taken to be rational as the counterparts of the rational magnitudes while the others that are surds are counterparts of the irrational magnitudes.

Among them (i.e., the mechanical sciences) also, are the many geometric (or engineering, handasiyya) mechanical sciences, such as:

The art of overseeing constructions (ṣināʿat riʾāsat al-bināʾ).

The devices for determining the areas of bodies.

The devices used in the production of astronomical and musical instruments, and in the preparation of instruments for many practical crafts (ṣanāʾiʿ) such as bows and arrows and various weapons.

The optical devices used in the production of instruments that direct the sight in order to discern the reality of the distant objects, and in the production of mirrors upon which one determines the points that reverse the rays by deflecting them (taʿṭufahā) or reflection (taʿkusahā) or refraction (taksurahā).With this, one can also determine the points that reverse the sun’s rays unto other bodies, thus producing the burning mirrors and the devices connected with them.

The devices used in the production of marvelous objects, and the instruments for the several crafts (ṣanāʾiʿ).

These and their likes are the mechanical sciences which (in turn) are the principles (mabādiʾ) of the civil and practical crafts that are applicable to bodies, shapes, positions, order, and assessments such as in the crafts of masonry, carpentry and others.⁹¹

Greco-Hellenistic concepts feature prominently in al-Fārābī’s discussion. His characterisation of mechanical sciences as an area where ideas or principles shift from potentiality to tangible reality aligns with Aristotle’s definition of skill (τέχνη), which embodies the transformative nature of knowledge into observable craftsmanship.⁹² Further, al-Fārābī’s distinction between theoretical an practical mechanical disciplines as well as the more organized approach to technological knowledge echoes the opinion of the Alexandrian school and, especially, of Hero and Pappus of Alexandria, whose texts had been translated into Arabic from the third/ninth century onwards. In the eighth book of the Collectio, Pappus delineates several manual activities, including metalworking, carpentry, architecture, and painting, as the practical components of mechanics, while also incorporating geometry, arithmetic, astronomy, and physics as its theoretical elements.⁹³

Al-Shaṭawī

The available information regarding AbÅ« Ê¿Abdallāh Muḥammad b. al-Ḥasan b. AkhÄ« Hishām al-Shaá¹­awÄ« is quite limited and relies solely on Ibn al-NadÄ«m, who places him among the lesser-known younger scholars specialising in astrology and geometry.⁹⁴ It is likely that al-Shaá¹­awÄ« was active during the first half of the fourth/tenth century. The list of his writings counts five books on various types of sundials, astronomy, and mechanics. In this field, he is credited with a treatise on mechanics or mechanical devices called Kitāb al-Ḥiyal, and another on water clocks, á¹¢anÊ¿at al-banādiq (Techniques of Balls). Based on the title of the latter work, it can be inferred that it dealt with the construction of one or more timekeeping devices using pebbles, similar to a type of clepsydra found in an Arabic treatise attributed to Archimedes (also cited by Ibn al-NadÄ«m) and in later works by al-MurādÄ«, Riḍwān al-SaʿātÄ«, and al-JazarÄ«.⁹⁵ Several examples of this kind of devices feature small balls that fall and strike a cymbal, signalling the transition from one hour to the next. Unfortunately, none of al-Shaá¹­awī’s works are currently known to be in existence.

Ibn al-Haytham

AbÅ« Ê¿AlÄ« al-Ḥasan b. al-Ḥasan b. al-Haytham (d. ca. 430/1040) was a Basran mathematician, physicist, and engineer, best known for his notable work in optics. Much of our understanding of his life and contributions is derived from the writings of Ibn al-Qifá¹­Ä« and Ibn AbÄ« Uá¹£aybiÊ¿a.⁹⁶ Initially employed in the Buyid governorate’s secretariat in Baá¹£ra during the Abbasid caliphate, his intellectual prowess soon gained recognition. His reputation reached the Fatimid court in Cairo, where it was said that he had a solution for controlling the Nile’s ebb and flow. Impressed by his abilities, the Fatimid caliph al-Ḥākim (r. 386–411/996–1021) invited him to Egypt. Ibn al-Haytham then relocated to Cairo and assumed the role of chief engineer for the Fatimid court. He led an expedition to survey potential dam sites along the Nile, though he ultimately found his design unworkable. Upon returning to Cairo, he admitted the limitations of his proposal to the caliph, who reassigned him to a symbolic role. Feeling vulnerable due to the whims of his patron, Ibn al-Haytham feigned madness, residing in seclusion until the caliph’s death. He spent the remainder of his life in Cairo.

According to Ibn AbÄ« Uá¹£aybiÊ¿a, who claims to quote from a list written by Ibn al-Haytham himself in the year 429/1038, he produced nearly 200 treatises covering topics such as optics, mathematics, astronomy, medicine, and chemistry. These works included two notable pieces on mechanics: Maqāla fÄ« l-qarasá¹­Å«n (On the Steelyard) and Maqāla fÄ« Ê¿amal al-binkām (On the Operation of the Water-Clock).⁹⁷ Additionally, in the context of timekeeping devices, he is also credited with two works on sundials. The first is dedicated to the construction of horizontal dials and it is addressed to the craftsmen who create them, while the second focuses on a universal theory of dials.⁹⁸

For this study, I will focus solely on Maqāla fÄ« Ê¿amal al-binkām. To the best of my knowledge, this concise treatise on a water clock is preserved in three manuscripts currently housed in Istanbul: two at the Süleymaniye Library and the third one at the Askeri Müze, or Military Museum.⁹⁹ In addition, the contribution of Ibn al-Haytham to the field of water clock is also attested by al-KhāzinÄ« (d. after 525/1130–1) in his Kitāb MÄ«zān al-ḥikma.¹⁰⁰

Maqāla fī ʿamal al-binkām introduces a model of an inflow water clock that, according to Ibn al-Haytham, was an innovative timekeeping device capable of measuring hours and minutes — apparently, a feature not found in other clocks of his time. At the beginning of the work, the author himself emphasised that many versions and models of water clocks had been developed before his time. However, unsatisfied with them, he devised a new design. His mechanism involved a sinking copper cylinder with a small hole at its base, which would descend into an outer cylindrical tank filled with water. As the cylinder sank, a string attached to it would rotate a circular disc marked with twenty-four divisions for hours and subdivisions for minutes. Consequently, Ibn al-Haytham carefully calibrated the sinking speed so that it would sink in twenty-four hours. To maintain uninterrupted and accurate tracking of time, he designed two identical clocks placed side by side. As one clock approached the end of its twenty-four-hour cycle, the second clock would initiate its cycle in synchronisation, thus allowing for continuous timekeeping.

Maqāla fī ʿamal al-binkām is a fundamental source for the history of timekeeping devices and water clocks in the early Islamicate world. In fact, it is one of the earliest-known treatises on the subject, alongside the Arabic treatise attributed to Archimedes and the three other most significant known works on the subject are from a later period: Kitāb al-Asrār fī natāʾij al-afkār by the Andalusian al-Murādī, Kitāb al-Jāmiʿ bayn al-ʿilm wa-l-ʿamal al-nāfiʿ fī ṣināʿat al-ḥiyal by al-Jazarī and Risāla fī ʿamal al-sāʿāt wā-stiʿmālihā (On the Construction of Clocks and Their Use) by Riḍwān al-Saʿātī. It is therefore highly desirable that Ibn al-Haytham’s work becomes the subject of a thorough study in the near future.

Hibat Allāh al-Badīʿ al-Asṭurlābī

Abū l-Qāsim Hibat Allāh b. al-Ḥusayn b. Aḥmad, also known as Badīʿ al-Zamān al-Asṭurlābī (d. 534/1139–40), dedicated his life to the pursuit of various fields, including astronomy, medicine, philosophy, and poetry. His acclaim stems from his expertise and skill in crafting astronomical instruments, particularly astrolabes. Later in his life, he relocated to Baghdad, where he flourished under the patronage of the caliph al-Mustarshid (r. 512–29/1118–35), achieving significant recognition.

While primarily celebrated for his exceptional command of astronomical instruments, al-BadiÊ¿ al-Asá¹­urlābī’s interests also extended to the field of mechanical studies. Surprisingly, this facet of his endeavours often goes unmentioned in historical accounts, but it gains substantiation through a significant source — the engineer al-JazarÄ«. Within his monumental work, al-JazarÄ« highlights al-BadÄ«Ê¿ al-Asá¹­urlābī’s contributions by commending his creation of a musical automaton in a dedicated chapter concerning the perpetual flute.¹⁰¹ Before presenting the details of his own invention, al-JazarÄ« examines earlier designs reminiscent of it, drawing references from Apollonius, an anonymous scholar, and Hibat Allāh BadÄ«Ê¿ al-Asá¹­urlābÄ«:

I also came across a treatise, authored by the distinguished inventor Hibat Allāh b. al-Ḥusayn al-Asá¹­urlābÄ« in Baghdad in the year 517 Hijri [approximately 1123 CE], in which he truly excelled. Its design is [as follows]: it has a cylindrical receiver with a lead ball in it, with an arm similar to a balance-arm, and two pans suspended by chains. It features three basins, six ground valves, and two pipes resembling the end sections of bows, coming out from different parts of the basins. This is a well-known device.¹⁰²

Al-Jazarī’s account serves as a testament to Hibat Allāh’s interest in mechanical contrivances. Not only does he make mention of his creation of a musical device, but he also underscores its distinction as a renowned prototype of a perpetual flutist. Furthermore, he connects it with the Greek scholar Apollonius and acknowledges both as authorities in the construction of musical automata.¹⁰³ Within these concise passages, one can discern that Hibat Allāh conceptualised this apparatus in Baghdad during the year 517/1123. Consequently, it is plausible that it was tailored for aristocratic circles and patrons, possibly including the Abbasids.

Yūnus al-Asṭurlābī

Little is known about the life of YÅ«nus b. al-Ḥusayn al-Asá¹­urlābÄ« and his potential connections to the Abbasid courtly settings. Due to the scarce information available, I have chosen to briefly discuss his work and contributions. YÅ«nus al-Asá¹­urlābÄ« is primarily recognised as the creator of a celestial globe, which is currently preserved in the Louvre.¹⁰⁴ The globe features an Arabic inscription indicating his name and the construction date, specifically the year 539/1144–5. Regrettably, the inscription does not reveal the location of its creation. Marcel Destombes posits that the artefact in question originated in Baghdad or, more likely, in Seljuk Iran.¹⁰⁵ Intriguingly, the oeuvre of YÅ«nus b. al-Ḥusayn al-Asá¹­urlābÄ« garners particular attention, given that his name is among the select few cited in al-Jazarī’s treatise. In the first section of the text, which focuses on clocks, al-JazarÄ« references and provides a succinct description of YÅ«nus’ candle clock model, which he had the opportunity to examine. His assessment of YÅ«nus’ candle clock is notably critical:

I have come across a clock from the work of YÅ«nus al-Asá¹­urlābÄ«, may God have mercy on him, and it has the appearance [of the clock] I have described in the introduction of the first design.¹⁰⁶ A cross-beam has a hole in the middle in which the wick is placed in the place of the container, which I took to prevent the candle from rising, and I found that the candle flowed into the interior of the sheat and over the instruments inside the sheat. In reality, the construction with the cross-beam is not valid at all. Then I found the weight in a different position from where I had placed it, and the two pulleys on which the weight was hanging were at half the height of the sheat. [There was] a rising rod on which the candle was placed above. This gave much trouble; for this reason, the design was useless, its failure to be due to the dripping wax. So, I made what I shall describe [now].¹⁰⁷

Firstly, al-JazarÄ« observes that YÅ«nus’ creation bears a striking resemblance to the device presented in the preceding chapter, specifically the seventh chapter of the first section of the book, rather than the first chapter as he erroneously mentioned.¹⁰⁸ This latter is a candle clock, primarily designed to measure night hours using a wax candle. It comprises a tall brass candle holder adorned with a falcon perched near its base and a slave figure holding a sword on a bracket towards the top. The candle, placed within a brass sheath, burns, and lifts a weight, causing the candle to rise. After an equinoctial hour passes, the falcon releases a ball from its beak, which falls onto the floor of the candle holder’s pedestal. The slave figure then strikes the wick with a sword, removing the burnt portion. This process repeats hourly until the morning, with the night’s hours determined by the number of balls in the pedestal.

From al-Jazarī’s treatise, it is clear that he had access to a written account solely dedicated to Yūnus’ clock. In fact, at the beginning of the seventh chapter, he mentions that he had never encountered any work on candle-clocks or seen a completed example of such a clock. It is also evident that he attempted to reproduce Yūnus’ candle clock but faced failure. This led him to critically evaluate the design, identifying it as a failed device due to wax overflow, which impacted the weight and pulleys. As a result, al-Jazarī proposed an innovative design featuring a brass sheath on a candle holder with an upright falcon at the bottom and a scribe on a dais to the right, holding a pen on the fifteen divisions of a complete circle.

Scholars often identify YÅ«nus al-Asá¹­urlābÄ«, as mentioned by al-JazarÄ«, with the Egyptian astronomer and mathematician Ibn YÅ«nus.¹⁰⁹ In support of this hypothesis, a short treatise on a candle clock attributed to Ibn YÅ«nus is cited, which has survived in a single copy and is currently held in the Saint Joseph Library in Beirut.¹¹⁰ This writing, however, presents a very different model of candle clock from the one described by al-JazarÄ«. It is, in fact, a chandelier with twelve lamps, so arranged that if all lamps are lit at sunset, one lamp will extinguish itself at the end of each of the twelve hours of the night.¹¹¹

Given the significant differences between the two models and the lack of known information that could lead us towards one or the other, it is only possible to consider several potential scenarios. First, the two models could have been created by two distinct individuals: one working in Egypt in the fourth/tenth century and the other possibly in Baghdad or Iran in the early sixth/twelfth century, each developing a different study on the candle clock. Alternatively, the YÅ«nus mentioned by al-Jazari might indeed be the Egyptian intellectual Ibn YÅ«nus. In this case, the two differing candle-clock models could suggest his dedication to studying and developing this type of device. Lastly, the twelve-armed chandelier model could also be the work of YÅ«nus al-Asá¹­urlābÄ« rather than Ibn YÅ«nus. Based on the celestial globe, it appears that he was a skilled instrument maker, who could plausibly be the inventor of the clock mentioned by the Artuqid scholar.¹¹² Furthermore, the treatise suggests that the candle clock was likely used at a latitude of thirty-five degrees, which is consistent with the latitude attributed to Babylonia by both Ptolemy and part of the oldest Arabic tradition.¹¹³ This location is more closely associated with YÅ«nus al-Asá¹­urlābī’s area of expertise than with that of Ibn YÅ«nus.

An Anonymous Baghdadi Water Clock?

The manuscript 4871, housed in the ẒāhirÄ«yya Library in Damascus, comprises a collection of philosophical and scientific texts covering a range of subjects.¹¹⁴ Produced in Baghdad during the sixth/twelfth century, it is believed to have been crafted by the same anonymous scribe over an estimated period of eight years.¹¹⁵ Of particular interest are two brief extracts that explore the field of mechanical devices.

The first extract, titled á¹¢anÊ¿at al-ālat al-zamriyya li-ĪliyÅ«s al-ḤakÄ«m (The Construction of the Whistling Instrument by ĪliyÅ«s the Sage), focuses on a fluting machine. The author’s name, ĪliyÅ«s the Sage, may be a mistranscription of AbulÄ«nÅ«s or Apollonius, who, as previously mentioned, is often cited in relation to musical automata.¹¹⁶

The second extract is an anonymous text dedicated to a water clock, called Ê¿Amal al-á¹£andÅ«q li-l-sāʿāt (The Operation of the Hour Box). Spanning three pages (ff. 77a–78a), this section includes a few drawings that illustrate the mechanism. The water clock described appears to be a ball-dropping model, complete with a semicircular zodiacal dial. While information about the text, the water clock itself, and the circumstances of its creation and usage is sparse, the limited details provided do establish connections with earlier and later examples of similar devices. Both the ball-dropping mechanism, used to indicate the passage of hours, and the zodiacal dial are common features found in Hellenistic and Islamicate clocks. For instance, this is evident in the clockworks attributed to Ctesibius and described by Vitruvius, as well as the first model of water clocks presented in al-Jazarī’s treatise.¹¹⁷

The Timekeeping Device at the Mustaná¹£iriyya Madrasa in Baghdad

A similar water clock to the one presented in the previous paragraph is mentioned in Baghdad, dating back to a few decades before the city’s fall to the Mongols in 656/1258. This clock was associated with one of the most prestigious religious and scholarly institutions of that period, the Mustaná¹£iriyya Madrasa. At the onset of his reign, al-Mustaná¹£ir billāh (r. 623–640/1226–1242), the second-to-last Abbasid caliph, commissioned the construction of this school on the left bank of the Tigris River. This institution was a beacon of Sunni orthodoxy, as one of the pioneering establishments hosting representatives from the HanafÄ«, MālikÄ«, ShāfiÊ¿Ä« and ḤanbalÄ« schools. Under the patronage of al-Mustaná¹£ir, who gave his name to the building, the madrasa was meant to embody a universal standing. The clock further reinforced this image by featuring representations of the heavens and celestial order. ¹¹⁸

The madrasa was well-equipped with facilities such as a hospital and pharmacy, a library dedicated to manuscript study and reproduction, and a monumental timekeeping device located over the courtyard entrance. Our understanding of the water clock is due to the accounts provided by contemporary sources, namely the Persian scholar Zakariyyāʾ al-QazwÄ«nÄ« (d. 682/1283), and the anonymous text al-Ḥawādith al-jāmiÊ¿a wa-l-tajārib al-nāfiÊ¿a fÄ« l-miʾa al-sābiÊ¿a (The Collected Events and Useful Experiences that Occurred in the Seventh [i. e. 13th] Century), previously ascribed to the Baghdadi historian Ibn al-Fuwaá¹­Ä« (d. 723/1323).¹¹⁹

Al-QazwÄ«nÄ«, who visited Baghdad toward the end of al-Mustaná¹£ir’s reign, chronicled the presence of the clock in his geographical gazetteer Āthār al-bilād fÄ« l-akhbār al-Ê¿ibād (Remnants of the Regions and Reports of the Righteous). In this text, he also shares verses about the water clock, attributing them to the renowned jurist and scholar AbÅ« l-Faraj Ê¿Abd al-Raḥmān Ibn al-JawzÄ« (d. 597/1201). However, as Ibn al-JawzÄ« passed away before al-Mustaná¹£ir’s accession to power, it is more likely that these verses were penned by one of his sons, specifically AbÅ« Muḥammad YÅ«suf (d. 656/1258). YÅ«suf himself had ties to the Mustaná¹£iriyya Madrasa, having served there as a teacher of ḤanbalÄ« law.¹²⁰ Al-QazwÄ«nī’s report states that:

One of the objects of pride [in Baghdad] is the school founded by al-Mustanṣir billāh. Nothing like it had been built before in terms of the beauty of its architecture, the elevation of its building, and the pleasantness of its site on the shore of the Tigris, with one of its facade in the water. No place was known to have more religious endowments than it, nor residents more wealthy than its own. At the school door, there is an iwan with mounted in its front, in a strange way, a clock box (ṣandūq al-sāʿāt), displaying the times of the prayers and the passing of the hours, at day and night. Abū al-Faraj ʿAbd al-Raḥmān ibn al-Jawzī said this:

In the anonymous Ḥawādith, the verses attributed to al-Jawzī are found with minor differences. Furthermore, the text offers a more detailed explanation of the clock’s appearance and operation:

In the wall of this room, a disc was built, and within it, an image of the celestial sphere was depicted. It included fine windows with fine doors. In the disc, there were two golden falcons, each inside a golden bowl, and behind them, two small metal balls that the observer could not notice. At the end of each hour, the falcons’ mouth opened, and the balls fell out. As each ball fell, a door from those windows would open, and the golden door appeared at that time silvered. When the balls fell into the bowls, they would return to their positions. Then, golden satellites would appear in the azure sky in that celestial sphere, rising with the real sun, revolving with its rotation, and setting with its setting. When night came, there would be moons rising, visible because of a light behind them. The light emitting from the disc of the moon would increase on the completion of a full hour. Then, it would begin in the other disc until the night elapsed, and the sun rose, so that the prayer times would be known. Poets composed poems about this, including a verse by AbÅ« al-Faraj Ê¿Abd al-Raḥmān ibn al-JawzÄ«, praising the Caliph in his lines.¹²²

Both sources detail a timekeeping apparatus designed for day and night use. During daylight, the device tracked time through a dual system: sound-based, with small pebbles released from the falcons into basins below, generating noise; and visual, by opening one of the windows. At night, hours were marked by light behind each of the disc apertures. The clock’s features place it within a longstanding horological tradition, including the Byzantine monumental clock in Gaza (sixth century CE), the Bāb JayrÅ«n clock located at the Great Mosque of Damascus, and al-Jazarī’s castle clock.¹²³