Megalethoscope Slide, "Milano Cathedral"

Invented by Carlo Ponti in the early 1860s, a megalethoscope is a device used to view a translucent, multilayered photograph. By opening or closing various panels, a person saw the image change. When lit from behind, pinpricks and paint or colored tissue applied to the back or a secondary layer of the photograph transform the scene to reveal hidden images and create an illusion of nighttime.