POSSIBLY MECCA, 15TH CENTURY

Al-Khayyami al-Nishapuri studied in Balkh and worked in Samarkand. In 1074 he was invited to the capital city of Isfahan by the Seljuk Sultan Jala al-Dawlah Malik Shah (1072-1092) to organise the astronomical observatory and reform the Iranian solar calendar which he completed in 1079. The new calendar consisted of 8 leap years for every 33 years and was called the 'Maliki' or the 'Jalali' era. The observatory was closed in 1092, and al-Khayyami went on to work for subsequent rulers including Sanjar (1118-1157) in Merv. He was a mathematician, astronomer and a great Persian poet as well as the author of political quatrains (ruba'i). This work is not listed in Rosenfeld and Ihsanoglu, it is almost certain to be al-Khayyami's work, Risalahfi'l barahin 'ala masa'il al-jabr wa'l-muqabala which the author worked in to verse (Rosenfeld and Ihsanoglu, Mathematicians, Astronomers & Other Scholars of Islamic Civilisation and their Works (7th-19th C.), Istanbul, 2003, no. 420, pp.168-70).