Columbia University Library MS Or 49,
Kitāb Uṣūl al-handasah wa-al-ḥisāb,
كتاب اصول الهندسة والحساب,
arabic translation of Euclid's Elements by Nasir ad Din at Tusi
copied in the mid- to late-19th century

fol 161, figure XIII.18



α               Σ                 ©