A thaumatrope is an optical toy that was popular in the 19th century. It featured a disk with a picture on each side that attached to two pieces of string. When the strings are twirled quickly between the fingers the two pictures appear to blend into one due to the persistence of vision.
Produced by John Ayrton Paris in England in 1824, the thaumatrope was the ancestor to other optical illusion instruments like the zoetrope or praxinoscope.
Size: The Thaumatrope includes 10 different, approximately 6.5 cm (2.56 inches) in diameter, discs, as well as a booklet with instructions and a history of the toy.