Quotation from: The Notebooks of Leonardo Da Vinci
Written by: Leonardo da Vinci
83.
OF THE PLANE OF GLASS.
Perspective is nothing else than seeing place [or objects] behind a
plane of glass, quite transparent, on the surface of which the
objects behind that glass are to be drawn. These can be traced in
pyramids to the point in the eye, and these pyramids are intersected
on the glass plane.