4. Leonardo Da Vinci, Mona Lisa (1503-1506) 77 x 53 cm

6. When his works were finished he [Apelles] used to cover them over with a black varnish of such thinness that its very presence, while its reflection threw up the brilliance of all the colors and preserved them from dust and dirt, was only visible to anyone who looked at it close up, but also employing great calculation of lights, so that the brilliance of the colors should not offend the sight when people looked at them as if through a seeing-stone [i.e., mica] and so that the same device from a distance might invisibly give somberness to colors that were too brilliant.
Pliny the Elder, Natural History,

12. Jorma Puranen, Shadows, Reflections, and All That Sort of Thing (2009) From left to right: 26, 30, 48.

13. By ‘images’ (eikona) I mean first shadows (skias), then reflections on water (phantasmata), and other close grained, polished surfaces, and all that sort of thing ….
Plato, The Republic, Book VII

15. Marcel Duchamp, L.H.O.O.Q. (1919)

16. Photograph of the Mona Lisa missing at the Louvre, 1911