An impossible figure representing a three-pronged (or two-pronged) object that emerged from an obscure source in the US in 1964 and appeared on the cover of Mad magazine in 1965 (see illustration). It has been incorporated into several of the paintings, drawings, and etchings of the Swedish artist Oscar Reutersvärd (1915–2002) and some of the works of the Dutch graphic artist Maurits C(ornelis) Escher (1898–1970). Also called a blivet. See also visual illusion.
Impossible trident. How many prongs does it have?