Sometimes depicted in writings and drawings from ancient classical, medieval, and modern times, the Zodiac Man (Homo Signorum or "Man of Signs") represents a roughly consistent correlation of zodiacal names with body parts. The Zodiac Man appeared most frequently in calendars, devotional Books of Hours, and treatises on philosophy, astrology, and medicine in the medieval era. Before the emergence of scientific empiricism in the 17th century, medieval physicians looked to the skies for guidance. Having observed that the overhead moon brought high tides, they theorized the dangers of letting blood from a body part whose zodiacal sign was occupied by the moon since a tide of blood might gush out uncontrollably. Table of correspondences The association of body parts with zodiac signs remained relatively consistent during antiquity and into the medieval period. The "primary" associations are both the oldest and the most common. Ancient origins The concept of the Zodiac Man dates to the Hellenistic era in which the earliest exposition appears in Manilius's Astronomica (II. 453–465; IV. 701–710). However, a cuneiform tablet of unknown date gives a nearly identical list of bodily divisions that possibly but not certainly could have been created before Manilius. A Greek text (περὶ μελῶν ζωδίων - On the limbs of the zodiacal sign) describing the subdivision of zodiac signs into dodecatemoria (signs within signs) suggests that Zodiac Man (or Zodiac Animal, modified slightly to suit each sign) could also be associated with the idea of this "micro-zodiac". Overall, the idea of Zodiac Man goes back thousands of years to Babylonia where the body was considered to work in tune with the heavenly bodies. The general system of zodiac signs relating to healing is thought to predate Manilius by several centuries and has been attributed to philosophers such as Pythagoras, Democritus, Aristotle, and Hermes. Astrological medicine The Zodiac Man was used in medieval medicine to determine the correct time for surgery, medication, bloodletting, and other procedures. The foremost rule was to avoid interfering with a body part when the moon could be found in its corresponding sign. This injunction was attributed to Claudius Ptolemy: "Membrum ferro ne percutito, cum Luna signum tenuerit, quod membro illi dominatur." Wherever the moon and stars are aligned with a certain astrological sign, they correlated with a body part, bodily system, or the four humors. The four humors separate the body into four parts just as there are four elements.