Watch as Grand Illusions‘ Hendrik Ball deftly showcases The Mephisto Spiral, a brain-breaking toy that seems to mix an optical illusion with a bit of the slight-of-hand skills required for magic tricks:
It looks like 2 interlocking wire spirals. In your hands, the two spirals seem to wind together or wind apart, completely effortlessly. However when you hand the Mephisto Spiral over to someone else, they find that they cannot replicate the action – the two wire spirals are completely rigid.
Alternatively, by simply moving your hands in one direction, you can make the two spirals appear to unwind, yet however many times you repeat the action, the two spirals never come apart.
How does this toy work? Here‘s another video example: