Derived from the Greek words, thauma meaning ‘wonder’ and tropos, meaning ‘turn,’ these ‘wonder-turners’ are optical illusion toys that illustrate the phenomenon of retinal persistence. As the disk spins, the images (or impressions of light) remain on the retina for a short time, allowing both images to be seen simultaneously as a complete image.

The concept of retinal persistence was first pondered by Aristotle and others including Leonardo and Newton. While many played with the idea of the thaumatrope, John Ayrton Paris is credited as the official inventor, in 1827. Often sold in sets, these paper disks were printed and hand colored. Many other optical toys soon followed the thaumatrope, and it is recognized as the predecessor to motion picture animation.