In this article I present the unique partial transmission of Euclid's Elements in the medieval Hebrew calendrical treatise Yesod 'Olam (The Foundation of the World ), which was composed by Isaac Israeli in 14thโcentury Toledo. After a short introduction of Yesod 'Olam , I discuss the role of mathematics, as understood by Israeli, in the study of astronomy and the Jewish calendar. I then provide a mapping of the Elements found in Yesod 'Olam and demonstrate Israeli's peculiar rendition of this seminal Greek work through four examples. Finally, I show that Israeli's transmission of the Elements is lexically independent of earlier known Hebrew versions of the text
