Abraham bar Hiyya ha-Nasi אברהם בר חייא הנשיא

Hibbur ha-Meshihah ve-ha-Tishboret is a book on measuring land and reckoning areas. Plato of Tivoli translated it into Latin, and through that translation Arabic mathematics entered Christian Europe; the book contains a complete solution of the quadratic equation—by present reckoning the first to reach the Latins.

He wrote also on the soul (Hegyon ha-Nefesh), on the terms of redemption (Megillat ha-Megalleh, where the count comes out at the year 5118), and on the calendar (Sefer ha-Ibbur). With Judah ben Barzillai he disputed whether a wedding once fixed might be put off on an astrologer's sign—an argument in which one sees how far apart two learned men of one city could stand.

The sources give no year of birth. The year of death is inferred from a manuscript dated 10 April 1136, where the scribe adds the formula for the dead to his name.