Jacob's ladder (toy)

When the ladder is held at one end, blocks appear to cascade down the strings.

It may be considered a kinetic illusion, where the blocks appear to change position when they do not.

[1] Of unknown origin, the earliest known review of the Jacob's Ladder is an 1889 Scientific American article which tells how it is built and works:[1] The simple toy ... is very illusive in action.

But this effect is only apparent, as the second block in reality only falls back into its original position in the series; but in the operation it becomes reversed, what was before the lower end becoming the upper end, the front having exchanged places with the back.

[1] Many slight variants have been patented in the United States, one from the 1940s having in one block an indentation to hold a penny, which then appeared to dis- and re-appear.