One of the enduring mysteries in the history of the Renaissance is the adult appearance of the archetypical "Renaissance Man," Leonardo da Vinci. His only acknowledged self-portrait is from an advanced age, and various candidate images of younger men are difficult to assess given the absence of documentary evidence. One clue about Leonardo's appearance comes from the remark of the contemporary historian, Vasari, that the sculpture of David by Leonardo's master, Andrea del Verrocchio, was based on the appearance of Leonardo
when he was an apprentice. Taking a cue from this statement, we suggest that the more mature sculpture of St. Thomas, also by Verrocchio, might also have been a portrait of Leonardo. We tested the possibility Leonardo was the subject for Verrocchio's sculpture by a novel computational technique for the comparison of
three-dimensional facial configurations. Based on quantitative measures of similarities, we also assess whether
another pair of candidate two-dimensional images are plausibly attributable as being portraits of Leonardo as
a young adult. Our results are consistent with the claim Leonardo is indeed the subject in these works, but
we need comparisons with images in a larger corpora of candidate artworks before our results achieve statistical significance.