Giovanni Antonio Magini (1555-1617). Full title: Io. Antonii Magini Patavini mathematicaum in almo Bononiensi gymnasio professoris de astrologica ratione, ac usu dierum criticorum, seu decretoriorum : ac præterea de cognoscendis & medendis morbis : ex corporum cœlestium cognitione, opus duobus libris distinctum : quorum primus complectitur commentarium in Claudij Galeni, librum tertium de diebus decretorijs, alter agit de legitimo astrologiæ in medicina usu : his additur de annui temporis mansura in directionibus: & de directionibus ipsis ex Valentini Naibodæ scriptis scriptis : ad seremissimum Mantuae & Montisferrati principem D. Franciscum Gonzagium [... on astrological reasoning, and the use of critical or decisive days: and moreover on the knowledge and healing of diseases: from the knowledge of the heavenly bodies, a work divided into two books: the first of which includes a commentary on Claudius Galen, the third book on in the days of the decrees, the other deals with the legitimate use of astrology in medicine: to these is added the keeping of the annual season in the directions: and the directions...]. Quarto: [10], 120 leaves. First edition of this treatise in which the author applies astrology to medicine, supporting its legitimate use but condemning its superstition. Typographic mark engraved on the title page, astrological diagrams and schematic engravings, historiated initials (restoration with additions to the title page without loss of text, scattered minor staining, leaf 68 with restoration at the lower margin, pronounced stains on leaves 97- 102, restoration to leaf 100 with small loss of text, marginal work of woodworms not touching the text with some restorations to the last papers). Complete. Modern binding restored in full vellum. Several engravings and diagrams in the text, all square in shape except that of page 64, which is circular and graphically anticipates the birth diagrams produced in later centuries. Provenance: several old underlines concentrated in the chapter on the power of the moon in announcing days of well-being and discomfort (leaves 20; 24). A wide ranging text, on critical days (days propitious or dangerous for medical interventions), with commentaries on Galen and lots of astro-medical case studies. Giovanni Antonio Magini (1555 – 1617) was an Italian astronomer, astrologer, cartographer, and mathematician. In 1588 he was chosen over Galileo Galilei to occupy the chair of mathematics at the University of Bologna after the death of Egnatio Danti. He died in Bologna. Magini supported a geocentric system of the world, in preference to Copernicus's heliocentric system. Magini devised his own planetary theory, in preference to other existing ones. The Maginian System consisted of eleven rotating spheres, which he described in his 'Novæ cœlestium orbium theoricæ congruentes cum observationibus N. Copernici' (Venice, 1589). Like most medical and other astrologers, Magini retained a Earth-centered cosmography. Magini's main work in this line is listed here as a defence of its use in medicine. Magini collaborated closely with Valentine Naibod, as is clear from this book. An important figure, Magini corresponded with Tycho Brahe, Clavius, Abraham Ortelius, and Johann Kepler. His correspondence was edited in 1886 by Antonio Favaro.