Sketches Revealed Underneath Leonardo's 'Virgin of the Rocks'
cnn.com
cnn.com
Michelangelo and Leonardo were asked to paint large (7x17 meters, or ~ 23 x 56 feet) murals depicting two important battles (the Anghiari one being assigned to Leonardo). The "cartone" [3] used by Michelangelo survived to this day. [4]
[0]: UC San Diego Researchers in Florence Explore New Ways to Search for Lost Leonardo Mural
[1]: https://www.ted.com/talks/maurizio_seracini_the_secret_lives...
[2]: https://en.wikipedia.org/wiki/Battle_of_Anghiari
[3]: https://it.wikipedia.org/wiki/Cartone_(arte) (couldn't find the one in English)
[4]: https://en.wikipedia.org/wiki/Battle_of_Cascina_(Michelangel...