Géométrie Stéréométrique

Two rare and curious items relating to the 19th-century epistemological shift in the teaching of geometry, which provided a way of conceiving the form of three-dimensional bodies through the use of folding printed cardboard models of polyhedra. Cardboard models of solids were cheaper than the wooden ones and could be folded, unfolded and refolded to form several combinations, such as pyramids, cubes, blocks, cylinders, cones, planes, and so forth.