The Impossible Triangle is an
optical illusion, first attributed to Swedish artist,
Oscar Reutersvärd, in 1934. Originally, he drew the shape with strings of cubes, rather than solid bars.
The more familiar version (shown below) was created independently by Roger Penrose after attending a lecture by Dutch artist, M. C. Escher in 1954.
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Escher, in turn, was inspired to create images, including his famous
"Waterfalls" image, by the work of the Penroses.
In 1980, the Swedish government honoured Reutersvärd by using his original image on a stamp between 1982 and 1984.