The practice of isometrical perspective
This is a mid-nineteenth-century London drawing manual on isometric perspective, written by Joseph Jopling and George Gladwin and published by M. Taylor in 1842 for students of technical drawing. Its pictures are line engravings of cuboid and prismatic solids with dashed construction lines and hatched shading, and a designer might take from them a clear method for showing sloped planes and cut-away geometry in three-dimensional wireframe views.
