"On his return, Protogenes noticed the line and, recognizing the hand of Apelles, drew on top of it another line in a different color, even more subtle than the first, thus making it appear as if there were three lines on the canvas. Apelles returned the next day, and the subtlety of the line he drew then made Protogenes despair. That work was for a long time admired by connoisseurs, who contemplated it with as much pleasure as if, instead of some barely visible lines, it had contained representations of gods and goddesses."
See also Chuang-tzu and Giotto.
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