Perspective Machines, Zograscopes, Megalethoscopes, and Boites d’Optiques

In the 18th century, there was a craze for special viewing devices that used large lenses, through which viewers looked at engraved scenes. It was claimed that such devices could produce a lively and almost three-dimensional image. But how could they get a stereo effect with only a single picture and a single lens, and no way to provide perspective information? Several such elaborate and expensive items can still be found in several museums.