According to artist and biographer Giorgio Vasari, Leonardo da Vinci was "so delighted when he saw curious heads, whether bearded or hairy, that he would follow anyone who had thus attracted his attention for a whole day, acquiring such a clear idea of him that when he went home he would draw the head as well as if the man had been present."
Take a closer look at the sketch here. Leonardo depicted the man's hair with his characteristic sfumato. The hatching lines slant downward from left to right, running in the natural direction for the left-handed artist.
He made this caricature, as one of a large series of head studies created in pairs. Years after the artist's death, collectors cut the pairs into individual drawings. This sketch measures just 6.6 x 5.4 cm (2 5/8 x 2 1/8 inches - smaller than a square post-it note, Many later artists admired and copied Leonardo's caricatures, both in drawings and prints.