Born into a family of Jewish translators of religious and philosophical writings from Arabic into Hebrew, Jacob ben Machir ibn Tibbon (Prophatius Judaeus) studied medicine at the University of Montpellier. Translated into Hebrew many scientific texts in Arabic by Muslim authors (Ibn al-Haytham, al-Zarqâlî, Jâbir ibn Aflah, ibn Rushd) and ancient Greek authors (Autolycos, Euclid, Menelaus of Alexandria). In c. 1290, wrote Roba' Yisrael, in which he described a new type of astrolabe quadrant. In c. 1300, compiled an Almanach of planetary motions. Jacob ben Machir is traditionally regarded as the inventor of an instrument for astronomical measurements known as cross-staff or Jacob's staff.