The first epigraph opening this chapter is taken from Vitruvius' De Architectura, a compendium of architectural practice from the first century bce with enduring influence in Western architecture. Vitruvius states that architects “should take the greatest care to master” symmetry while designing a temple. A precise definition of symmetry is, however, missing from this text. We are instead told that the respect of symmetry passes through observing some proportions between the constituent parts of what is designed. The instance chosen by Vitruvius to exemplify this observance of proportions was the human body, and the proportions respected by nature, in the case of “a well-formed human being”, have the form of simple ratios between lengths in the body, as in “the face, from the chin to the top of the forehead […] should be one-tenth [of the total height of the body]”. This set of canonical proportions was the source of one of the most celebrated drawings of Leonardo da Vinci.