Perspective is the method of sketching a front with the sides withdrawing into the background, the lines all meeting in the center of a circleWhile he doesn't elaborate on that, elsewhere in his book, his reference to Greek and Roman stage design seem to imply an understanding of the vanishing point.
The Roman author Pliny the Elder, who died in the eruption of Mount Vesuvius in 79 CE, told of the discovery of the art of drawing by a Corinthian girl, Dibutade, who traced the silhouette of her lover as it was projected onto a wall by the light of a single flame.
This legend is illustrated below
The Invention of Drawing, Francois Boucher, 1703-1770