Impossible trident

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 described the novelty as follows: "Unlike other ambiguous drawings, an actual shift in visual fixation is involved in its perception and resolution.

"[5] The word "poiuyt" appeared on the March 1965 cover[6] of Mad magazine bearing the four-eyed Alfred E. Neuman balancing the impossible fork on his finger with caption "Introducing 'The Mad Poiuyt' " (the last six letters on the top row of QWERTY 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, 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[7]).

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.