Wollaston type camera lucida, 1806-1820.

The Wollaston camera lucida is a drawing aid that an artist can use to accurately delineate an object or landscape being sketched. In operation, the user views the scene to be sketched by looking down onto the mirror or prism. By looking to one side of the device the user sees both the paper and scene, a view that the brain fuses together. William Hyde Wollaston (1766-1828), the famous English scientist, first devised the split-pupil form of the camera lucida around 1800. Granted at British patent in 1806 his design was rapidly adopted by instrument makers around the world.