device that uses a prism and mirrors to project the image of an object onto a flat surface so that it may be traced
an optical device consisting of an attachment that enables an observer to view simultaneously the image and a drawing surface for sketching it
An instrument which by means of a prism of a peculiar form, or an arrangement of mirrors, causes an apparent image of an external object or objects to appear as if projected upon a plane surface, as of paper or canvas, so that the outlines may conveniently traced