First and only edition of an important work on spherical sundials by the Dutch mathematician Johann Hermann Knoop (1700-1769). It describes how to measure and construct different types of sundials, including one inside a hollow half sphere, and a "gnomic" armillary sphere. The plates, engraved by Jan Caspar Philips (1690-1775), depict these sundials. They are bound at the end of the text and can be folded out while consulting the text.
Knoop was curator of the gardens of Princes Maria Louisa in Leeuwarden, and taught mathematics in the same city.With two small stamps and a shelf label on title-page. Title-page browned and thumbed, with a water stain in the foot margin, margins slightly browned throughout, with a few small spots. Otherwise in good condition, wholly untrimmed and with most bolts unopened. Binding in very good condition. Bierens de Haan 2521.