rth.

Now Paolo was for ever investigating, without a moment's intermission,
the most difficult problems of art, insomuch that he reduced to
perfection the method of drawing perspectives from the ground-plans of
houses and from the profiles of buildings, carried right up to the
summits of the cornices and the roofs, by means of intersecting lines,
making them foreshortened and diminishing towards the centre, after
having first fixed the eye-level either high or low, according to his
pleasure. So greatly, in short, did he occupy himself with these
difficulties, that he introduced a way, method, and rule of placing
figures firmly on the planes whereon their feet are planted, and
foreshortening them bit by bit, and making them recede by a
proportionate diminution; which hitherto had always been done by chance.
He discovered, likewise, the method of turning the intersections and
arches of vaulted roofs; the foreshortening of ceilings by means of the
convergence of the beams; and the making of round columns at the salient
angle of the walls of a house in a manner that they curve at the corner,
and, being drawn in perspective, break the angle and cause it to appear
level. For the sake of these investigations he kept himself in seclusion
and almost a hermit, having little intercourse with anyone, and staying
weeks and months in his house without showing himself. And although
these were difficult and beautiful problems, if he had spent that time
in the study of figures, he would have brought them to absolute
perfection; for even so he made them with passing good draughtsmanship.
But, consuming his time in these researches, he remained throughout his
whole life more poor than famous; wherefore the sculptor Donatello, who
was very much his friend, said to him very often--when Paolo showed him
mazzocchi[10] with pointed ornaments, and squares drawn in perspective
from diverse aspects; spheres with seventy-two diamond-shaped facets,
with wood-shavings wound round sticks on each facet; and other
fantastic devices on which he spent and wasted his time--"Ah, Paolo,
this perspective of thine makes thee abandon the substance for the
shadow; these are things that are only useful to men who work at the
inlaying of wood, seeing that they fill their borders with chips and
shavings, with spirals both round and square, and with other similar
things."

[Footnote 10: Mazzocchi are probably coronets placed on the arms of
noble families; also c