KEPLER, Johannes (1571-1630). Phaenomenon singulare seu Mercurius in Sole. Leipzig: printed by Tobias Beyer for Thomas Shurer, 1609.

First edition of one of the rarest Kepler titles. On the 28th of May, 1607, Kepler observed the sun by letting its light pass through a tiny aperture in a darkened room. With this method, he observed a small black dot passing over the sun’s surface, which he believed to be the transit of Mercury. However, shortly after this work was published, improvements in telescopes led to the first European observations of sunspots. Galileo claimed to have discovered them in the summer of 1610, and Thomas Harriot certainly had seen them by the end of 1610. Kepler quickly realized his mistake and this slim volume appears never to have achieved wide circulation. The folding plate depicts Kepler’s camera obscura apparatus. Kepler also includes an elegy on the death of his friend’s daughter who died just two days after the observation. Caspar 30.

Quarto (194 x 141mm). Text ornaments and a few woodcut diagrams; one folding plate. Includes final blank leaf. (Browned.) Modern quarter calf over marbled boards. Provenance: Owen Gingerich (bookplate).