Claudius Ptolemy (trans. J. M. Ashmand, 1822) · c. 150 CE · English (from Greek via Proclus paraphrase)
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Contents — 70 chapters
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About this book
The Tetrabiblos ("Four Books") is Ptolemy's 2nd-century CE exposition of astrological judgement — the companion to his Almagest, treating the planets and zodiac as a system of natural causes. Across four books and seventy chapters it sets out the elements of interpretation: planetary natures, zodiacal powers, aspects, dignities, and the logic of mundane and natal prediction.
Relevance to this project
The astronomical backbone of the project — the 7 planets and 12 zodiac signs that the Sefer Yetzirah maps to the 7 double and 12 simple Hebrew letters — is exactly the frame Ptolemy codifies. The Tetrabiblos is the source from which Arabic, Hebrew, and Renaissance astrology (and the Picatrix) inherited the planetary-period and sign-correspondence structure the paper's sky readings are computed from.
