Anamorphic pictures, c.1750.
Anamorphic pictures using mirrors were fairly common in the eighteenth century. Demainbray used them, along with other optical toys, to open his course on optics. A cylindrical mirror is placed on top of a distorted picture. When viewed from above, the picture is instantly recognisable. Other distorted images viewed through the side of a conical mirror show sililar effects.
© Science Museum/Science & Society Picture Library