Sermo mirabilis

Sermo mirabilis, or, the silent language whereby one may learn in the space of six hours, how to impart his mind to his Friend in any Language, English, Latin, French, Dutch, & tho never so deep and dangerous a Secret, without the least Noise, Word or Voice; and without the Knowledge of any in the company. Being an art kept secret for several ages in Padua, and now made published only to the wise and prudent, who will not expose it, as a Prostitute, to every Foolish and Ignorant Fellow. By Monsieur La Fin, once secretary to His Eminence, Cardinal Richlieu, by Charles La Fin, 1692. (Action on Hearing Loss Library). Charles de la Fin or La Fin (1640s-1690s?) used different parts of the body to indicate letters, so 'L' was represented by the lip, 'W' by the wrist etc. The vowels were the same as in modern British fingerspelling, indicated by the thumb & fingers. La Fin describes in his book how he taught a young gentleman the art, who was then able to use it to woo a lady in the presence of her family.

La Fin was, according to the book, sometime secretary to Cardinal Richelieu (d.1642), and according to More good and true news from Ireland where a letter from him to his brother James appears, he was "page to the young Prince of Orange" who was later William II, Prince of Orange, father of William III. James was secretary to the exiled French Duke of Valette. The dedication to William & Mary shows him to have been a firm supporter of the House of Orange.