Leonardo da Vinci is known almost as well for his many inventions
as for his world -renowned fresco of the Last Supper in the refectory of Sta. Maria della Grazie in Milan.

The Leonardo exhibition in Rome has modern copies of many of these inventions, including this simplified representation
of a perspective device to enable artists to more accurately represent perspective in their paintings.
When one looks through the hole in the center of the board, a grid aids inlining up various aspect of the view.
(see next image).

in the late 15th c., Leonardo described a "camera obscure", which involved using a pinhole device in a dark room with a mirror.
This device was continually perfected by other artists and scientists to make increasingly more accurate depictions of perspective.