A Dentist Discovered a Hidden Code in Leonardo da Vinci’s Most Famous Drawing

The 1490 illustration was originally created to demonstrate a principle theorized by the Roman architect Vitruvius—that the human body could proportionally fit within both a circle and a square. However, the image contains more than just this well-known concept.

A dentist observing the drawing noticed a third shape—a triangle formed between the figure’s legs—that was reminiscent of a dental principle known as Bonwill’s triangle.

This story is a collaboration with Biography.com.

Art, by its nature, often lends itself to multiple readings or interpretations. What one takes away from a work of art depends not just on what the artist intended when they sat down to put pen to paper or paint to canvas, but also on what the observer brings to the piece when they look upon it.

In his work *De architectura*, Vitruvius, the Roman architect, discussed the idea of the central navel as a focal point for human proportions.

The namesake Bonwill here is Dr. William Bonwill, whose 1864 work on the Articulation of the Teeth built upon the study of “4,000 dentures in living persons and 6,000 skulls” to establish a standard for denture shape. The Journal of the New York Institute of Stomatology described this shape as “an arch based on the equilateral triangle and conforming closely to the most perfect arches found.”

Of course, it would take a dentist to notice a principle of dentistry tucked away in Leonardo da Vinci’s drawing. But while the triangle’s relevance to Sweeney’s dental expertise was the initial impetus for his observation, it is not the only purpose he believes the shape serves in the work.

Noticing the other element requires going back to the work that predates even Leonardo da Vinci: the musings of Vitruvius on the idea of the central navel.

Sweeney posits that if one were to create five more triangles of equal dimension, all originating from that navel point, it would form a hexagonal pattern behind the ratio of approximately 1.64—a tetrahedral ratio—between the square’s side and the circle’s radius. Sweeney describes this as “a mathematical relationship that defines optimal spatial arrangements in both synthetic and biological systems.”

He even draws parallels between the ratios found in Leonardo’s illustration and Buckminster Fuller’s Isotropic Vector Matrix from 1975. Sweeney concludes that “the same geometric relationships that appear in optimal crystal structures, biological architectures, and Fuller’s coordinate systems seem to be encoded in human proportions, suggesting that Leonardo intuited fundamental truths about the mathematical nature of reality itself.”

**Topics:** Arts/Photography; History; Society; Weird Stuff

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