It was the year 1540 when Petrus Apianus, a German humanist noted for his impressive work in mathematics, cartography, and astronomy, published and dedicated this masterful work to Emperor Charles I of Spain and V of Germany. His interest in these sciences led the sovereign to finance the mysterious manual and, later, to become its patron, granting him titles in order to protect the opinions of an intellectual dangerously advanced for his time. The Astronomicum Caesarum is considered one of the masterpieces of 16th-century printing. Its lavish illustrations, designed on hand-colored cardboard movable discs sewn with thread, depict nothing less than the evolution of the universe and the laws that govern it. In it, Appian offers instructions for the use of the movable discs, or volvelles, with which he perfectly imitated the use of the astrolabe and which he used, for example, to calculate the exact birth dates of Charles I and his brother Ferdinand.
The work is recognized as one of the finest astronomical treatises of the 16th century due to the simplicity with which it attempts to explain these sciences to the reader, accompanied by lavish illustrations and diagrams. Furthermore, it managed to identify the trajectories of some comets, predict eclipses, and predict the royal horoscope. This was so unusual and surprising in the Renaissance period that it has survived and is appreciated to this day.
Art and science merge in this book, of which 111 copies are preserved worldwide. Only 25 of these are in perfect condition or with most of the movable discs or volvelles preserved. In 2020, at auction in the United States, one of these copies fetched $260,000.
This compendium of ideas on astronomy is presented in a simple manner with the sole intention of facilitating the reader's understanding, but without neglecting elegance and exquisiteness in form.
Thirty-five paper engravings with movable discs make up the print of a manual that has made history for its content and the visual richness evident on each of its pages.
Apianus, with his knowledge and the publication of this work, is undoubtedly part of a scientific revolution that in his time challenged God and the Church, and which over the centuries has become key to understanding the world and breaking with thinking based on divine laws.
A book is a treasure. And the Astronomicum Caesarum is a good example of this, both for its valuable content and the exquisiteness of its forms.
