* The golden section (also known as “golden ratio” or “divine proportion”) was defined by Euclid as the division of a line segment into two parts in such a way that the ratio of the whole segment to the larger part is equal to the ratio of the larger part to the smaller. In the Renaissance, the golden section was considered the proportion most pleasing to the eye, and many artists and architects incorporated approximate golden ratios into their works (see Livio, The Golden Ratio).

† Leonardo’s extensive studies of horses are assembled in a special volume of the Royal Collection at Windsor Castle; see p. 355 below.