EON DE BEAUMONT, Charles de, Chevalier (1728-1810). Lettres, memoires & negotiations particulieres ... aupres du roi de la Grande Bretagne. [The Hague], chez l'auteur, 1764. 4° (292 x 221mm), title in red and black, folding printed table, errata leaf at end, later red half roan (rubbed). FIRST EDITION of a remarkable volume of secret correspondence by one of the 18th century's most exotic players and one whose sex was a matter of considerable speculation. Until a jury in 1777 decided that there was sufficient evidence to prove that he was a woman the mystery had excited huge wagers. Certainly from 1785 until his death twenty-five years later D'Eon dressed as a woman, although his post-mortem revealed him to be a man.