The Mount of Mercury lies at the base of the little finger, and the tradition claims for it quickness of mind, eloquence, aptitude for commerce and for science, and, in the less flattering readings, cunning and a talent for deception; again the astrological significations of Mercury are transferred whole. The Mercury line, also called the health or hepatica line, rises from this region in most versions of the scheme. Palmistry divides into chiromancy, the reading of the lines, and chirognomy, the reading of the shape of the hand and fingers, a distinction Desbarrolles drew; d'Arpentigny's contribution was on the chirognomic side, with his classification of hands into seven types by shape.
Traditional chiromancy reads a well-developed Mount of Mercury, at the base of the little finger, as indicating quickness of mind, verbal skill, aptitude for commerce and science, and adaptability, drawn from Mercury's own classical association with communication, trade and cunning intelligence, the messenger god's own domain. An excessively developed mount is read as a tendency toward deceit or trickery, echoing Mercury's dual mythological reputation as both a helpful messenger and a trickster figure, while a flat mount suggests social awkwardness or difficulty with practical affairs. As with the other mounts in this scheme, the attribution rests on the tradition's own internal planetary symbolism rather than on any demonstrated connection between hand shape and personality.
Sources Les Mysteres de la MainAdolphe Desbarrolles with Introductiones apotelesmaticae elegantes in chyromantiam, physiognomiam, astrologiam naturalem, complexiones hominum, naturas planetarumJohannes ab Indagine (Johannes Rosenbach), La Chirognomonie, ou l'art de reconnaitre les tendances de l'intelligence d'apres les formes de la mainCasimir Stanislas d'Arpentigny