A short note on Ptolemys motivation for the introduction of the equant in Almagest X based on his planetary observations. This is Section II.8 of al-Shīrāzī’s Nihāyat al-idrāk fī dirāyat al-aflāk, but in the MSS Edinburgh, EUL, Or. 397 and Mashhad, Holy Shrine, 5452 it is found as an independent work appended to al-Ṭūsī’s Taḥrīr al-Majisṭī (C.1.18). The version extant in Edinburgh differs slightly from that in the other witnesses: it lacks a heading, but provides an additional criticism of Ptolemy’s method at the end (cf. the edition in Gamini & Masoumi Hamedani, p. 67).

Origin: Al-Shīrāzī finished his Nihāyat al-idrāk in Sivas in Shaʿbān 680/November-December 1281 (Niazi). However, MS Oxford, BL, Thurston 3 is dated 660/1262, with some parts copied in 675/1277. It was written by al-Shīrāzī’s disciple or close collaborator Suhrāb b. Amīr al-Ḥājj, the same scribe who also copied MS Leiden, UB, Or. 203, a copy of the Nihāyat al-idrāk dated 682/1283. In Thurston 3, as well as in Mashhad, Holy Shrine, 5452, the method presented in this treatise is ascribed to Thābit b. Qurra (for which, however, there seems to be no evidence in the extant works by Thābit, see Gamini & Masoumi Hamedani, p. 61). Assuming that Suhrāb was well informed about the works of al-Shīrāzī, it seems most plausible that al-Shīrāzī first wrote a short treatise on Ptolemy’s equant following a method already employed by Thābit b. Qurra and later inserted it into his Nihāyat al-idrāk.

Text: [Oxford, BL, Thurston 3]

(101v–102r) إنّ بطلميوس أخذ بالرصد في سنين متوالية مقدار الرجوع أعني الدرج التي يرجع فيها الكوكب من فلك البروج من الوقوف الأوّل إلى الوقوف الثاني. — ولأنّه استخرج الحركات والنسبة المذكورة من جداول القدماء قبل التصحيح قال في كتابه إنّه وجد هذا الخطّ ضعف هذا الخطّ بالتقريب. وهو أعلم بالسرائر إنّه هو العليم الحكيم.

[Edinburgh, EUL, Or. 397]

[alternative explicit] (235r) إنّ بطلميوس إنّما حكم بكون مركز الحاملين مركزي المعدّل ومعدّل المسير. ظنّا منه بأن فرضه بينهما وهو عليه فلمّا وافق محسوبة المرصود إطمان إلى ذلك وسبب ذلك أنّ هذا البرهان لم يذكر في المجسطي ولم يشتهر اشتهارًا غيره. تمّت والحمد لله شكرًا له.

Bibl.: SuterHeinrich Suter, Die Mathematiker und Astronomen der Araber und ihre Werke, Leipzig: Teubner, 1900, pp. 158–159 (no. 387); GAS VIFuat Sezgin, Geschichte des arabischen Schrifttums. Vol. VI: Astronomie bis ca. 430 H., Leiden: Brill, 1978, p. 90 (no. 5c) and p. 168; F. Jamil Ragep, ‘Shīrāzī’s Nihāyat al-Idrāk: Introduction and Conclusion’, Tarikh-e Elm 11 (2013), pp. 41–57; Amir Mohammad Gamini and Hossein Masoumi Hamedani, ‘Al-Shīrāzī and the Empirical Origin of Ptolemy’s Equant in His Model of the Superior Planets’, Arabic Sciences and Philosophy 23 (2013), pp. 47–67; Kaveh Niazi, Quṭb al-Dīn Shīrāzī and the Configuration of the Heavens. A Comparison of Texts and Models, Dordrecht: Springer, 2014, esp. p. 85; Fateme Savadi, The Historical and Cosmographical Context of Hayʾat al-arḍ with a Focus on Quṭb al-Dīn Shīrāzī’s Nihāyat al-Idrāk, PhD dissertation, McGill University, 2018, esp. pp. 21–44 and 107–108.

Ed.: Critical edition, based on the Mashhad manuscript and two manuscripts of the Nihāyat al-idrāk, in Gamini & Masoumi Hamedani, pp. 64–67, with an English translation on pp. 61–64.