I was introduced to this optical illusion in the early 70s in a book called Perplexing Puzzles and Tantalizing Teasers, a book I checked the hell out of from the local library. I've always loved this thing.
(h/t +Asbjørn Grandt)
Originally shared by +Bjarne Panduro Tveskov:
"When Escher met IKEA"
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