I have had the good fortune to acquire a copy of Georges Hébert's book on "Quadrupédie", the art of movement on four limbs, which is part of his master works on physical education with the natural method, published in 1946 in French and sadly never re-edited or translated.
I already did some fan dub translation on a earlier book which appeared on Google Books, so I thought I should at least collect a few notes and excerpts from this new book, which might be the most unusual and overlooked part of his teachings, although it has come back quite a bit with the growth of Parkour. All of this is of course purely subjective (even when I quote Hébert directly, I am still selecting a quote) and incomplete. I'll try to include some of the excellent technical drawings he had made, which tell a lot by themselves.
These quadrupedal techniques are not arranged as a series of exercises or in progression of skill, but rather described logically and exhaustively, grouping together movements of variable difficulty but related form of execution. Be mindful of this if you want to "try it at home", and make sure you understand the potential risks and difficulties involved. That being said, a lot of quadrupedal exercises are very efficient at building strength and flexibility for the whole body, and provide safety mechanisms in potentially dangerous situations.