The respected French art historian, André Chastel, in ‘L’illustre incomprise’, 1988, emphasises the thesis of Maurice H. Goldblatt. Goldblatt’s thesis, 60 states that:
“ … only in the authentic paintings of Leonardo da Vinci do we find that the line of the mouth of a smiling female face was drawn on the arc of a circle, which, when extended, will just touch the outer corner of one or both eyes, according to the position of the head. Also, when the head is uncovered, as in the Mona Lisa and the Edwards Madonna, the outline of the head is the arc of another circle twice the diameter of the first circle.”
A thorough examination seems to show that the earlier version of ‘Mona Lisa’ fits Goldblatt’s thesis more precisely than any other female portrait by Leonardo da Vinci.