An impossible trident, also known as an impossible fork, blivet, poiuyt, or devil's

tuning fork A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs (tines) formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it against ...

,Brooks Masterton, John M. Kennedy
"Building the Devil's Tuning Fork"
''Perception'', 1975, vol. 4, pp. 107-109 is a drawing of an

impossible object An impossible object (also known as an impossible figure or an undecidable figure) is a type of optical illusion that consists of a two-dimensional figure which is instantly and naturally understood as representing a projection of a three-dimen ...

(undecipherable figure), a kind of an

optical illusion Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide v ...

. It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end. In 1964, D.H. Schuster reported that he noticed an ambiguous figure of a new kind in the advertising section of an aviation journal. He dubbed it a "three-stick

clevis A clevis fastener is a two-piece fastener system consisting of a ''clevis'' and a ''clevis pin head''. The clevis is a U-shaped piece that has holes at the end of the prongs to accept the clevis pin. The clevis pin is similar to a bolt, but is ...

". He described the novelty as follows: "Unlike other ambiguous drawings, an actual shift in visual fixation is involved in its perception and resolution." The word "poiuyt" appeared on the March 1965 cover of '' Mad'' magazine bearing the four-eyed

Alfred E. Neuman Alfred E. Neuman is the fictitious mascot and cover boy of the American humor magazine '' Mad''. The character's distinct smiling face, parted red hair, gap-tooth smile, freckles, protruding nose, and scrawny body, first emerged in U.S. iconog ...

balancing the impossible fork on his finger with caption "Introducing 'The Mad Poiuyt' " (the last six letters on the top row of

QWERTY QWERTY () is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on a layout created f ...

typewriters, right to left). An anonymously-contributed version described as a "hole location gauge" was printed in the June 1964 issue of ''

Analog Science Fiction and Fact ''Analog Science Fiction and Fact'' is an American science fiction magazine published under various titles since 1930. Originally titled ''Astounding Stories of Super-Science'', the first issue was dated January 1930, published by William C ...

'', with the comment that "this outrageous piece of draftsmanship evidently escaped from the Finagle & Diddle Engineering Works" (although something else called a "hole location gauge" had already been patented in 1961). The term "blivet" for the impossible fork was popularized by ''

Worm Runner's Digest The ''Worm Runner's Digest'' (''W.R.D.'') was created in 1959 by biologist James V. McConnell after his experiments with memory transfer in planarian worms generated a torrent of mail enquiries. The ''W.R.D.'' published both satirical articles, s ...

'' magazine. In 1967 Harold Baldwin published there an article, "Building better blivets", in which he described the rules for the construction of drawings based on the impossible fork. In December 1968 American optical designer and artist

Roger Hayward Roger Hayward (1899 – October 11, 1979) was an American artist, architect, optical designer and astronomer. He is the inventor of an early Schmidt-Cassegrain camera that was patented in 1945. He was born on January 7, 1899, to mother, artist I ...

wrote a humorous submission "Blivets: Research and Development" for ''The Worm Runner's Digest'' in which he presented various drawings based on the blivet. He "explained" the term as follows: "The blivet was first discovered in 1892 in Pfulingen, Germany, by a cross-eyed dwarf named Erasmus Wolfgang Blivet."''Science, Sex, and Sacred Cows: Spoofs on Science from the Worm Runner's Digest'', 1971
pp. 91-93
/ref> He also published there a sequel, '' Blivets — the Makings''.

Notes

{{Optical illusions Optical illusions Impossible objects Military humor