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13 Dhu’l Qa‘da 813 AH (9 March 1411 AD)

Naṣīr al-Dīn al-Ṭūsī was a prolific philosopher, scientist, and theologian who is often considered to have created the discipline of trigonometry. His 150 compositions and translations include a work on the astrolabe, an Arabic version of Euclid’s *Elements*, and the *Tadhkira fi ‘ilm al-ha’a* (*Memorandum of Astronomy*), in which he corrected inconsistencies in the Ptolemaic system. In this thirteenth-century recension of the *Almagest*, he updates several of Ptolemy’s methods, substituting later trigonometric equations for Ptolemy’s chord calculations and condensing the calculation of each planet’s equant (the point around which its epicycle revolved) into a single example with variable parameters. Also included in this codex is the 1304-5 commentary on this text by Iranian astronomer Niẓām al-Dīn al-Nīsābūrī. Many of the diagrams in this manuscript are illuminated, with gold leaf often extending beyond the precise outlines of the under-drawings (e.g. fols. 4v, 37r, 168r).

UPenn LJS 392

156r-157v

Persia (?)

Arabic

Muḥammad Ibn al-Ḥusayn al-Ḥasan

Paper

213

264 x 166 mm

17th-century morocco with flap and blind-stamped medallion

Crofton Black, ed., *Transformation of Knowledge: Early Manuscripts from the Collection of Lawrence J. Schoenber*g (London: Paul Holberton, 2006), 54-5.