An impossible trident, also known as an impossible fork, blivet, poiuyt, or devil's tuning fork,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 In 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 varie ...

. 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''. Terms 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 ...

". 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, gap-toothed smile, freckles, red hair, protruding ears, and scrawny body date back to late 19th-century ad ...

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 letter row of the keyboard: . The QWERTY design is based on a layout included in the Sh ...

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 Cla ...

'', with the comment that "this outrageous piece of draftsmanship evidently escaped from the Finagle & Diddle Engineering Works". Subsequently, a correspondent revealed that he had encountered the type of figure about twenty years previously, and had used it as a business logo since 1952. 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, ...

'' 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 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