The most familiar image of this doctrine is the homo signorum or zodiac man, a diagram of a human figure with the sign glyphs or animals disposed over the corresponding parts, which appears in medieval manuscripts, in the illuminated calendars of books of hours, and in vast numbers in the printed almanacs of the fifteenth to nineteenth centuries. Its practical purpose was to warn against bloodletting or surgery on a part of the body while the Moon stood in the sign governing it, a rule that was standard medical caution in Europe for centuries and appears in surgical texts as well as in popular almanacs. The figure survived in almanacs long after educated medicine had abandoned the theory, and versions were still being printed in the nineteenth and even the twentieth century. It is recorded here as a real and consequential episode in the history of medicine, not as guidance.
The single most celebrated version of the image appears in the Tres Riches Heures du Duc de Berry, painted by the Limbourg brothers around 1412 to 1416 for Jean, Duc de Berry, and left unfinished at their deaths; it shows two figures, one facing forward and one from behind, with the sign glyphs set over the corresponding parts of each, an image found in no other book of hours and generally read as reflecting Berry's own particular interest in astrology. In English almanacs the figure, often called the Man of Signs, appeared in roughly three-quarters of all almanacs printed by 1760, a share that fell to about a third by the century's end as Enlightenment-era printers began adding sceptical commentary alongside it; some almanacs, including the modern Old Farmer's Almanac, still print a version of the figure today.
Sources AstronomicaMarcus Manilius with The Zodiacal Miniature of the Tres Riches Heures of the Duke of Berry: Its Sources and MeaningHarry Bober, Astrology and the Popular Press: English Almanacs 1500-1800Bernard Capp