ʿIsa Tarsah Kelemechi[1] was a Church of the East astronomer and physician[2] at the Yuan court of Kublai Khan's Mongol Empire in the 13th century.
ʿIsa was named head of the Office of Western Astronomy established by Kublai Khan in 1263 to study Islamic astronomical observations.[3] Kubilai would establish a Observatory for Islamic astronomy in 1271, directed by astronomer Jamal ad-Din Bukhari.[3]
ʿIsa was also instrumental in reinforcing anti-Muslim prohibitions in the Mongol realms, such as prohibiting halal slaughter and circumcision, and, according to Rashid-al-Din Hamadani encouraged denunciation of Muslims.[4] ʿIsa also showed to Khubilai the Sword Verse of the Quran, raising the suspicion of the Mongols towards Muslims.[4] According to Rashid al-Din, as a result, "most Muslims left Khitai [China]".[4]
Isa Kelemechi was later a member of the first mission to Europe sent by Arghun, the Il-Khan in 1285. He met with Pope Honorius IV, remitting a letter from Ghazan offering to "remove" the Saracenz and divide "the land of Sham, namely Egypt" with the Franks.[5] [6] The message, written in imperfect Latin, said:
The 1285 embassy would be followed in 1287 by that of Rabban bar Sauma.[5]