Perspectiua horaria, siue, De horographia gnomonica tum theoretica, tum practica libri quatuor ...
Perspectiua horaria is a 1648 Roman treatise on sundials and perspective by the French Minim friar Emmanuel Maignan, written for mathematicians and instrument makers. Its pictures are geometric diagrams of lettered points, arcs and planes, with a sundial-like dial and a sphere drawn in outline, which a designer could use as clean technical line figures for compass-and-ruler constructions.
