One of the popular toys in Overton’s Curios is the thaumatrope. As Calyx is looking through his inventory sheets one day, he decides to order more of them from London, projecting that they will sell steadily throughout the summer. What are they, exactly?

Look at something. Now look at something else.

The bird and cage, a common theme for nineteenth century thaumatropes.

For a fraction of a second, your eyes held onto the first image you looked at. That’s not long enough to make much of a difference to you in your daily life, but if you could move your eyes back and forth from one object to the other ten to twenty times a second, you would see both things at the same time, as if they were in the same exact place. This is called persistence of vision.

The thaumatrope, invented in 1826 by an English physician named John Ayrton Paris, uses that principle to trick your brain into thinking it sees two things at once. Paris took a disc and drew a bird on one side and a birdcage on the other. Then he attached string to each end of the disc and quickly spun it. While the disc was in motion, the two sides appeared simultaneously as a bird inside a birdcage.

Joseph Plateau’s phenakistiscope.

The word thaumatrope comes from two Greek words: thauma (wonder or magic) and trope (turn).

In the nineteenth century, these wonderturns became popular toys, commonly featuring simple sketches of the bird and cage or a bare tree on one side and its leaves on the other. Animation as we know it hadn’t been invented yet, but this sort of thing caught the attention of aspiring cinematographers of the day, who uses other principles of vision (along with this one) to invent more advanced toys. Just six years after the thaumatrope came about, a Belgian physician named Joseph Plateau invented the phenakistoscope, which was a rotating disc with a series of images that created the illusion of movement. Animation was officially born.

Here’s a modern adaptation of the “bird in a cage” thaumatrope:

And here’s a really creative, cool one of a… flying buzzard bat? This one can be spun a little more slowly to create the illusion of motion: