Video:
In any case, Mona Lisa is a breakthrough in portraiture and fully deserves its reputation, one so great that people line up to see the painting up close, for all of fifteen seconds. Six millions per year.
The power of a cultural icon.
And, a lesson in what we think we know. END
PS: A documentary video:
(Notice in this video an emphasis on Leonardo's musings in his 4,000 pp of unpublished notes, on fossils and related ideas that were later picked up in Geological thought. This summary gives some details, and here, here and here in context in the IOSE give some balancing thoughts.)
