Camera lucida

A camera lucida is an optical device used as a drawing aid by artists.
The camera lucida was patented in 1807 by William Hyde Wollaston. The basic optics were described 200 years earlier by Johannes Kepler in his Dioptrice (1611), but there is no evidence he or his contemporaries constructed a working camera lucida. By the 19th century, Kepler’s description had totally fallen into oblivion, so Wollaston’s claim was never challenged.

http://en.wikipedia.org/wiki/Camera_lucida