© Science Museum / Science & Society Picture Library
Hand coloured lithograph with paper viewing flap attached with sewing, published by I Dickinson (114 New Bond Street, London). An horisontorium is an optical device, similar to an anamorphosis, which is a distorted image that appears corrected when viewed in a particular way. A scene of a roadside cottage behind a church tower is shown with a woman and child at the door and animals and a soldier nearby, all drawn in distorted perspective. The viewing point is centrally marked. The viewer peers through a hole in the attached flap, whilst keeping the image flat, to view the image with a 3-D effect.