TWO VOLUMES BOUND TOGETHER of the astronomical work `Yesod Olam`, the best contribution on that subject to Hebrew literature much studied in the Middle Ages, written by the renowned medieval Spanish-Jewish astronomer Isaac Israeli ben Joseph in 1310 at the request of his teacher Asher ben Yehiel. The `Yesod Olam` was first published at Berlin, in 1777, by Jacob Shklower, and a more complete edition was published with a preface by David Cassel, by B.Goldberg and L.Rosenkranz in 1846-48. Contains 4 b&w schemes and various illustrations throughout the pages, as well as a printed dedication to Moses and Judith Montefiore from the publishers. 42 last pages are b&w tables. 250x200mm. [XXXVIII+60] + 47 double pages & 42 pages. Quarter-cloth marbled Hardcover. Cover edges worn and bumped. Spine slightly stained. Ex-Libris of the Jewish National and University Library on front inner cover. Stamp on title page and between page 42 and schemes (not on text). Binding visible between pages 25-26 of the second volume. Pages yellowing, wavy and age-stained. [SUMMARY]: This extremely rare book is otherwise in good condition.