CLAVIUS, Christophorus. Romani Calendarii a Gregorio XIII. P.M. restituti Explicatio S.D.N. Clementis VIII. P.M. iussu edita. Roma, Luigi Zanetti, 1603

Folio, mm. 340x230; Full vellum binding, golden title on the spine; device of Pope Clement VIII on Title-page, Illustrated Initials and woodcut ornaments. Ownership note on the Title-page: "P. Andreae Eudaemon, Ex dono auctoris”. Sign of dampstain on the corners, slight sign of browning and humidity in the last part of the text.

First edition of the prestigious provenance. Pope Gregory XIII appointed Clavius as Prime mathematician in the pontifical commission established to reform the Julian calendar, which took effect in 1582: in this work, the eminent Jesuit publishes the new calendar, he explains the reasons for the reform and especially defends it against attacks of theologians Protestants and scientists such as Michael Mästlin, Joseph Justus Scaliger and François Viète. Gillispie: “The Gregorian calendar met up with a great deal of opposition from scientists such as Viète and Scaliger and from the Protestants.” This specimen was donated by the author to the philosopher and theologian Andreas Eudaemon-Joannes, who puts his signature on the Title page: the illustrious family of Crete related to the Paleologi, entered the Society of Jesus in 1583 and was a professor in the college of Rome, Padua and Naples, and finally rector of the College Greek and theologian of Cardinal Barberini in Rome. He wrote several books and devoted himself particularly to the philosophy of nature and philosophy of science while staying in Padua had frequent discussions with Galileo. Gillispie, D.S.B., III, p. 312; Sommervogel, II, col. 1218, n. 11; Honeyman, n. 717. About Eudamon, see: C.E. O'Neill - J.M. Dominguez, Diccionario Histórico de la Compañía de Jesús, II, P. 1343; Sommervogel, III, Col. 482. W.A. Wallace: Galileo and his sources; the heritage of the Collegio Romano in Galileo's Science, Princeton, 1984. The Lot is offered with a valid export licence.