Astrolabium Planum

This is Johannes Angelus's Astrolabium Planum, printed at Augsburg by Erhard Ratdolt in 1488, an early printed astrological reference carrying an illustrated image for each of the 360 degrees of the zodiac. As a primary printed text from the incunabula period it is the correct source for what this particular astrological image tradition actually depicted and how it was organized. Its limit is that it is a technical reference work compiling a symbolic system rather than an argument for astrology's validity or a historical study of the tradition's origins, so a claim about where this degree-symbol system itself came from needs a separate historical source, and the work's standing rests on its documented printing history rather than on any claim about astrology's predictive accuracy, which it does not itself argue for.