"Vitruvian derives from the name of a Roman architect called Vitruvius, who wrote and worked in the 1st century BC, " says Lester. Vitruvius, in a book on architecture, described the ideal human form that "could be made to fit inside a circle and could be made to fit inside a square. "
Vitruvius thought of that ideal human body as a blueprint for universal design, and if you studied it, you could "latch on to the design principles that made both the human body and the universe perfect." He then proposed that architects who understood that design could use it to create perfect buildings.
His idea was so captivating that though he didn't illustrate his concept, many people tried. "Especially in the 15th century, in the decades leading up to Leonardo's own time in drawing, a number of people begin to try to render that idea in visual form, " says Lester. But da Vinci's drawing is the one that stuck.