Prince Rupert's Cube/Historical Note

Historical Note on Prince Rupert's Cube

According to John Wallis, the puzzle now known as Prince Rupert's Cube was first posed by Prince Rupert of the Rhine in $1693$.

The correct answer was determined by Pieter Nieuwland.

An incorrect solution to this puzzle, often quoted in the literature, was provided by Wallis himself, who assumed that the tunnel in question would be parallel to the space diagonal of the cube.

This provides a solution of $\sqrt 6 - \sqrt 2 \approx 1 \cdotp 03527$.