Michelangelo did not paint the Sistine Chapel lying down.
From 1508 to 1512, Michelangelo painted the roughly 500-square-metre ceiling of the Sistine Chapel, even though he considered himself a sculptor. He worked standing on scaffolding he designed himself, head bent backwards. In a mocking poem he complained about his twisted neck and paint dripping onto his face.
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Source: en.wikipedia.org