Nasir al-Din Tusi Day · Ruz-e Khajeh Nasir

Culture of origin: Iranian · Cultural

Holiday sources: Iran

Nasir al-Din Tusi (1201–1274), born in Tus in Khorasan, was a Persian polymath who wrote on astronomy, mathematics, philosophy and ethics. After the Mongols took Alamut in 1256 he entered Hulagu Khan's service, helped save libraries from destruction, and persuaded Hulagu to build the observatory at Maragheh, begun in 1259. He is often credited with making trigonometry a discipline of its own.