A circle surrounded by a square looks larger than the same circle surrounding a square.
Square-in-a-Circle Illusion
See also
Circle, Square, Square IllusionsThis entry contributed by Margherita Barile
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References
Carraher, R. G. and Thurston, J. B. Optical Illusions and the Visual Arts. New York: Reinhold, 1966.Referenced on Wolfram|Alpha
Square-in-a-Circle IllusionCite this as:
Barile, Margherita. "Square-in-a-Circle Illusion." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/Square-in-a-CircleIllusion.html