The Anthology of Vettius Valens is a second century Greek compendium of working Hellenistic astrological technique, the fullest surviving record of how astrologers of that period actually practiced their craft, publicly available in its Teubner edition. As a primary ancient text it sits at this atlas's top tier for documenting what Hellenistic astrology taught and how it was cast, not for whether any of it describes something real. It is strong evidence for the technical content of ancient practice. Its date is approximate, as is usual for ancient technical writing transmitted through later manuscript copies, and a claim about how a given technique changed after Valens needs a source tracing that later development.