Sculptured figures which appear in motion, will, in their standing position, actually look as if they were falling forward.
[Footnote: figure di rilievo. Leonardo applies this term exclusively to wholly detached figures, especially to those standing free. This note apparently refers to some particular case, though we have no knowledge of what that may have been. If we suppose it to refer to the first model of the equestrian statue of Francesco Sforza (see the introduction to the notes on Sculpture) this observation may be regarded as one of his arguments for abandoning the first scheme of the Sforza Monument, in which the horse was to be galloping (see page 2). It is also in favour of this theory that the note is written in a manuscript volume already completed in 1492. Leonardo’s opinions as to the shortcomings of plastic works when compared with paintings are given under No. 655 and 656.]
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.