Before photography, cameras, computer vision and facial recognition, in 1807 Sir William Hyde Wollaston invented Camera Lucida - an optical aid to help artists create realistic drawings. Around that time lenses and mirrors were the "cutting edge technology" of their day (and sometimes, the trade secret) for making life-like images. Wollaston's Camera Lucida was simple: a prism on an adjustable stand. When an artist looks down through the prism, they see the world in front of them, plus their hand on the page, combined in a perfect superimposition. By the mid-1800s, camera lucidas were everywhere and the device was so effective in assisting accurate life-drawing that, according to the controversial Hockney-Falco hypothesis, it's now believed that many of the most admired drawings of the 19th Century, such as the Neoclassical portraits of Jean-Auguste-Dominique Ingres, could only have been made with a Camera Lucida. Unfortunately by the end of the century they were all gone and there was no Camera Lucida's manufactured since then. If you wanted to obtain one now it would cost you hundreds of dollars, thats if you can find one.