Manhattan's massive Metropolitan Museum has added a tiny new prize to its treasuresan 8 in. by 6⅛ in. drawing of the Virgin by Leonardo da Vinci. Done in black and red chalk on specially prepared paper, it was evidently a study for the Louvre's famed oil of The Virgin and Child with St. Anne; it has the left-to-right shading that left-handed Leonardo favored.
Most important, it shines with the Gioconda smile, tight yet tender, fleeting yet eternal, which was Leonardo's strangest and least imitable gift to human imagination. The drawing may have taken the artist no more than an hour to...