Is Leonardo da Vinci's "Head of a Young Woman" the greatest drawing ever made?

Granted, that may sound like a presumptuous question. Yet both the drawing and its subject — an ethereal young beauty who might easily pass for the Mona Lisa's kid sister or one of the elf-maidens in "The Lord of the Rings" trilogy — have had plenty of admirers over the years. The Renaissance art scholar Bernard Berenson, for example, called it "one of the finest achievements in all draughtsmanship."