Head of a Young Woman (La Scapigliata) by Leonardo da Vinci

In the Leonardo da Vinci's sketches, many parts are lost in obscurity, or are left intentionally uncertain and mysterious, even in the light, and you might at first imagine some permission of escape had been here given you from the terrible law of delineation. But the slightest attempts to copy them will show you that the terminal lines are inimitably subtle, un-accusably true, and filled by gradations of shade so determined and measured that the addition of a grain of lead or chalk as large as the filament of a moth's wing would make an appreciable difference in them.

There may not be in the world another example of a genius so universal, so inventive, so incapable of fulfillment, so full of yearning for the infinite, so naturally refined, so far ahead of his own century and the following centuries. Leonardo da Vinci's figures reveal incredible sensitivity and intellect; they are full of unexpressed ideas and feelings. Next to them, David by Michelangelo is mere a heroic athlete, The Sistine Madonna by Raphael only placid girl whose un-awakened soul has never know life.