Thumb, Fingers
Standing
Concerns Planetary Rulership
Currently States Mars, by the lower Mount of Mars, which lies above the thumb inside the curve of the life line
According To Western chiromancy
Johannes ab Indagine's 1522 chiromancy text, printed by Johannes Schott, Strasbourg, one of the foundational printed works of Western palmistry, sets out planetary rulership for the four fingers as a symmetrical four-part scheme, but the thumb sits outside that scheme from the start: its own mount at the base of the palm is assigned to Venus, while a separate Mount of Mars lies just above it within the life line. Later manuals, including the palmist Cheiro's, go further and set the thumb apart from the planetary fingers altogether rather than assigning it a fifth planet. Comparing the 1522 text against these later mounts shows the inconsistency is structural, not a later corruption: a four-finger, four-planet correspondence never had a built-in fifth slot for the thumb, which is why different sources in the tradition assign it differently and the atlas records the thumb under Mars while noting the mount at its base belongs to Venus.
Source Introductiones apotelesmaticae elegantes in chyromantiam, physiognomiam, astrologiam naturalem, complexiones hominum, naturas planetarum, Johannes ab Indagine (Johannes Rosenbach)