[PRESTET, Jean]. Elemens des Mathematiques ou principes généraux de toutes les sciences qui ont les grandeurs pour objet. Contenant un méthode courte et facile pour comparer ces grandeurs et pour découvrir leurs rapports par le moyen des caractères des nombres. 1675.

First edition.
"In the eighteenth century proofs were given of Descartes' Rule of Signs' which its discoverer had enunciated without demonstration.
G. W. Leibniz had pointed out a line of proof, but did not actually give it.
In 1675 Jean Prestet (1648-1690) publihed at Paris in his Elemens des mathematiques a proof." (Cajori) (page 368)
First proof of the Descartes' Rule of Signs'. Prestet afterwards acknowledged to be insufficient.
We had to wait 1828 and the work of Gauss to have a correct proof.
Fine copy.