his studies, and his brain should have the power of adapting itself to
the tenor of the objects which present themselves before it, and he
should be freed from all other cares. And if, while considering and
examining one subject, a second should intervene, as happens when an
object occupies the mind, he ought to decide which of these subjects
presents greater difficulties in investigation, and follow that until it
becomes entirely clear, and afterwards pursue the investigation of the
other. And above all he should keep his mind as clear as the surface of
a mirror, which becomes changed to as many different colours as are
those of the objects within it, and his companions should resemble him
in a taste for these studies; and if he fail to find any such, he should
accustom himself to be alone in his investigations, for in the end he
will find no more profitable companionship.

_Leonardo._


LI

If you are fond of copying other Men's Work, as being Originals more
constant to be seen and imitated than any living Object, I should rather
advise to copy anything moderately carved than excellently painted: For
by imitating a Picture, we only habituate our Hand to take a mere
Resemblance; whereas by drawing from a carved Original, we learn not
only to take this Resemblance, but also the true Lights.

_Leon Battista Alberti._


LII