[CARDANO, Girolamo. Opus novum de proportionibus numerorum, Basle: Henricus Petri, 1570]. 2°, woodcut initials, diagrams (lacking title and final leaf of text, light waterstaining to last few leaves, disbound), contemporary calf (covers detached, spine broken, worn). FIRST EDITION. Adams C689; Smith p. 338. Contains Cardano's major contributions to mechanics, and the revised second edition of the Artis Magnae, the most important contribution to algebra in the 16th century.