Tetrabiblos

Claudius Ptolemy · ~150 d.C.

A foundational treatise of Western astrology that established the basis of the system of 12 signs, houses and planetary aspects.

It divides astrology into four parts: general principles, universal predictions, natal predictions and predictions by place of origin.

The most influential astrological work in history. Ptolemy systematized Hellenistic astrology in four books that defined the practice for almost two millennia.