Ellipse Perspective: Halo from da Vinci's Annunciation, da Vinci's Gears (inverted), Flying Time)

From Draw Like da Vinci, p. 48: See how the radiating lines of the halo are shortest in the middle and gradually elongate towards the sides; the same foreshortening principle applies ot the numerals on the clock face. Leonardo draw gears with the light coming from above, and shaded the sides in shadow when the gears were positioned vertically (see also Ellipse Perspective: Coin, Can, Glass).