Optical Toys

A bird on one side of the disc, an empty cage on the other. Twirl it: it starts very slowly, so you can watch each side go by, then speeds up little by little. Or slide the speed yourself.

The thaumatrope (1825) was a disk with different images on each side—spin it and a bird appears inside a cage.

The thaumatrope was invented by John Ayrton Paris in 1825. Source: Science Museum Group

Optical toys like these were popular family entertainment in Victorian homes. Source: V&A