What was the original concept of Vitruvian man, according to Roman engineer and architect Vitruvius?

Vitruvius described ideal human proportions by showing that a man with his arms and legs extended could fit within a circle (and a square). The circle’s circumference would touch the hands and feet. The claims that a perfect man is seven heads long or exactly 6 feet 2 inches tall are not the concept described here.

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