HARTSOEKER, Nicolaas (1656-1725). Essay de dioptrique. Paris: Jean Anisson, 1694. 4o (245 x 179 mm). Woodcut text illustrations, engraved lunar plan by Duchange laid in between Z1 and Z2. (Light browning to quires X and Y, occasional minor spotting and very light marginal browning, small hole and torn corner to final blank). Contemporary speckled calf, spine gilt, red leather lettering piece (joints and extremities rubbed, boards very slightly worn). Provenance: Ludovici (engraved armorial bookplate on front pastedown); Pierre Lambert (small library label on front pastedown). FIRST EDITION. Hartsoeker was one of the earliest microscopists, working with Huygens in Paris during the 1670s. His telescopes were considered as perfect as those of Leeuwenhoek. Essay de Dioptrique discussed the anatomy of the eye, the physics of vision, the theory of color, and optical lenses. In addition to his work on lenses, Hartsoeker was interested in embryology; on p. 230 a woodcut of a spermatozoa shows a homunculus curled up inside, illustrating the author's belief that the fetus was preformed there. Hirsch III.77; Poggendorff I. 1026.