CLAVIUS, Christoph (1537-1612). Astrolabium. Rome: Bartholomaeus Grassius, 1593. Small 4° (218 x 156mm), large woodcut on title, numerous woodcut diagrams in the text (lacking the colophon leaf and final blank, lower inner margin of title torn away just touching text, a few leaves browned, waterstain in upper margin of some leaves, lightly spotted). Contemporary limp vellum (lightly soiled, rubbed). FIRST EDITION. Adams C 2093; Houzeau & Lancaster 3291: "Rare ... c'est dans cet ouvrage qu'on trouve le premier aperçu de la méthode de multiplication au moyen des fouctions circulaires, qui a reçu le nom de prostaphérèse."