Xerographic print on cardboard.
Squaring the circle refers to an ancient problem in geometry, to create a square and a circle with the same area, using only a compass and ruler. It became a metaphor for trying to do the impossible, as the problem was never solved, and it was only discovered to be unachievable in the late nineteenth century.
In alchemy, squaring the circle referred to a specific symbol that was a clue towards acquiring the philosopher's stone. The figure was a nested sequence of circle, square, triangle, circle.
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As with most alchemical language, it was actually a metaphor describing the unity of opposites. The diagram signifies body, soul, and spirit and was a lesson about wholeness, the unification of the self.