This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
A numerology system entry records one of the several distinct traditions, Pythagorean, Chaldean, Hebrew gematria, Greek isopsephy, Arabic abjad and Chinese numerology among them, that assign numeric value to letters, names or dates and read significance from the resulting figure, each with its own documented origin, its own alphabet or notation, and its own specific method of calculation that an entry keeps distinct from the others rather than treating numerology as one undivided practice.
Underwood Dudley's mathematical history examines the Pythagorean system specifically, tracing its actual documented origin to relatively recent popularizers working from the ancient reputation of Pythagoras himself rather than to any genuine antique source, and Dudley's own training as a mathematician lets the book assess plainly whether a given numerological claim about a number's properties is mathematically accurate.
An entry uses Dudley's history for the documented, checkable origin of the specific system it examines and for an honest account of which of its claims are mathematical fact and which are interpretive tradition, since the two are not the same kind of statement even within one numerology system's own literature, and an entry that blurs them misrepresents what the system itself is actually claiming.