Leonardo da Vinci's drawing of the vortices shed behind a blunt obstacle

Lenardo da Vinci's observation:
"Observe the motion of the water surface, which resembles that of hair, that has two motions: one due to the weight of the shaft, the other to the shape of the curls; thus, water has eddying motions, one part of which is due to the principal current, the other to the random and reverse motion."