A PICTURE OF OBJECTS IN PERSPECTIVE WILL LOOK MORE LIFELIKE WHEN
SEEN FROM THE POINT FROM WHICH THE OBJECTS WERE DRAWN.

If you want to represent an object near to you which is to have the
effect of nature, it is impossible that your perspective should not
look wrong, with every false relation and disagreement of proportion
that can be imagined in a wretched work, unless the spectator, when
he looks at it, has his eye at the very distance and height and
direction where the eye or the point of sight was placed in doing
this perspective. Hence it would be necessary to make a window, or
rather a hole, of the size of your face through which you can look
at the work; and if you do this, beyond all doubt your work, if it
is correct as to light and shade, will have the effect of nature;
nay you will hardly persuade yourself that those objects are
painted; otherwise do not trouble yourself about it, unless indeed
you make your view at least 20 times as far off as the greatest
width or height of the objects represented, and this will satisfy
any spectator placed anywhere opposite to the picture.

If you want the proof briefly shown, take a piece of wood in the
form of a little column, eight times as high as it is thick, like a
column without any plinth or capital; then mark off on a flat wall
40 equal spaces, equal to its width so that between them they make
40 columns resembling your little column; you then must fix,
opposite the centre space, and at 4 braccia from the wall, a thin
strip of iron with a small round hole in the middle about as large
as a big pearl. Close to this hole place a light touching it. Then
place your column against each mark on the wall and draw the outline
of its shadow; afterwards shade it and look through the hole in the
iron plate.

[Footnote: In the original there is a wide space between lines 3 and
4 in which we find two sketches not belonging to the text. It is
unnecessary to give prominence to the points in which my reading
differs from that of M. RAVAISSON or to justify myself, since they
are all of secondary importance and can also be immediately verified
from the photograph facsimile in his edition.]