The impossible fork (Seckel 2002, p. 151), also known as the devil's pitchfork (Singmaster), blivet, or poiuyt, is a classic impossible figure originally due to
Schuster (1964). While each prong of the fork (or, in the original work, "clevis")
appears normal, attempting to determine their manner of attachment shows that something
is seriously out of whack. The second figure above shows three impossible figures:
the ambihelical hexnut in the lower left-hand
corner, tribox in the middle, and impossible fork in the
upper right.
About the time of the impossible fork's discovery by Schuster (1964), it was used by Mad Magazine as a recurring theme. Their term for it was "poiuyt,"
which corresponds to the third row of a standard keyboard typed from right to left.
The "poiuyt" was commonly used in Mad throughout the 1960s indicating
absurdity or impossibility.
Hayward incorporated this figure into a picture of Greek columns (Gardner 1970, Robinson 1998).
