OF A MODE OF DRAWING A PLACE ACCURATELY.

Have a piece of glass as large as a half sheet of royal folio paper
and set thus firmly in front of your eyes that is, between your eye
and the thing you want to draw; then place yourself at a distance of
2/3 of a braccia from the glass fixing your head with a machine in
such a way that you cannot move it at all. Then shut or entirely
cover one eye and with a brush or red chalk draw upon the glass that
which you see beyond it; then trace it on paper from the glass,
afterwards transfer it onto good paper, and paint it if you like,
carefully attending to the arial perspective.

HOW TO LEARN TO PLACE YOUR FIGURES CORRECTLY.

If you want to acquire a practice of good and correct attitudes for
your figures, make a square frame or net, and square it out with
thread; place this between your eye and the nude model you are
drawing, and draw these same squares on the paper on which you mean
to draw the figure, but very delicately. Then place a pellet of wax
on a spot of the net which will serve as a fixed point, which,
whenever you look at your model, must cover the pit of the throat;
or, if his back is turned, it may cover one of the vertebrae of the
neck. Thus these threads will guide you as to each part of the body
which, in any given attitude will be found below the pit of the
throat, or the angles of the shoulders, or the nipples, or hips and
other parts of the body; and the transverse lines of the net will
show you how much the figure is higher over the leg on which it is
posed than over the other, and the same with the hips, and the knees
and the feet. But always fix the net perpendicularly so that all the
divisions that you see the model divided into by the net work
correspond with your drawing of the model on the net work you have
sketched. The squares you draw may be as much smaller than those of
the net as you wish that your figure should be smaller than nature.
Afterwards remember when drawing figures, to use the rule of the
corresponding proportions of the limbs as you have learnt it from
the frame and net. This should be 3 braccia and a half high and 3
braccia wide; 7 braccia distant from you and 1 braccio from the
model.

[Footnote: Leonardo is commonly credited with the invention of the
arrangement of a plate of glass commonly known as the "vertical
plane." Professor E. VON BRUCKE in his _"Bruchstucke aus der Theorie
der bildenden Kunste,"_ Leipzig 1877, pg. 3, writes on this
contrivance. _"Unsere Glastafel ist die sogenannte Glastafel des
Leonardo da Vinci, die in Gestalt einer Glastafel vorgestellte
Bildflache."_]