Eliphas Levi, 1861
Each letter is an universal and an absolute conception, governed only by the number represented by the letter. The science of signs begins with the science of letters.
Letters are absolute ideas. Absolute ideas are numbers. Numbers are perfect signs.
In using ideas with numbers, one can operate upon the ideas like one can operate upon number and arrive at the mathematics of truth.
(Course of Kabalistic and Occult Philosophy, The Kabalistic and Occult Tarot of Eliphas Levi, 1861)