Al-Risāla al-muḥīṭa : Nuskha-yi khaṭṭi-yi shumāra-yi 5389 Kitābkhāna-yi Āstān-i Quds-i Riḍawī

Ghiyāth al-Dīn Jamshīd Kāshānī is one of the most outstanding mathematicians and astronomers in the history of the Persianate world. The son of a physician, he was born around 790/1388 in Kashan, where he lived most of his life. Many of his writings were composed in that city, including his famous Zīj-i Khāqānī. In 824/1421 he left for Samarqand, where he played an important role in the construction of the observatory commissioned by the Timurid ruler and astronomer, Ulugh Beg (853/1449), becoming its first director. In 832/1429 he was found dead near this observatory, outside the walls of Samarqand. A violent death is suspected, probably on the order of Ulugh Beg. The present work, completed in 827/1424 in Samarqand, is about the determination of the number Pi. An innovative work of great merit, its exactness was only superseded with the publication of Ludolph van Ceulen's Van den circel in Delft, Holland, in 1596.