Tahrir al-Majisti
Naṣīr al-Dīn al-Ṭūsī was a prolific philosopher, mathematician, and theologian who is often considered to have created the discipline of trigonometry. His 150 compositions and translations include a treatise on the astrolabe, an Arabic version of Euclid’s <em>Elements</em>, and the <em>Tadhkira fi ‘ilm al-ha’a</em> (<em>Memorandum of Astronomy</em>), in which he corrected inconsistencies in the Ptolemaic system. In this 13th-century recension of the <em>Almagest</em>, he updates several of Ptolemy’s methods, substituting more advanced trigonometric equations for Ptolemy’s chord calculations and condensing the calculation of each planet’s equant (the point around which its epicycle revolves) into a single equation 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).
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Schoenberg Institute for Manuscript Studies
13 Dhu’l Qa‘da 813 AH (9 March 1411 AD)