Philip Melanchthon sends greetings to Simon Grynaeus, a most learned man and an old friend

Since it is beneficial in all arts to teach some brief elements at the beginning in order to prepare students for deeper knowledge, the greatest gratitude is due to the most excellent and learned men who wrote introductory works for us of those most beautiful disciplines, that is, of astronomy and cosmography. They deserve praise not only because of the merit of the arts themselves, but even more because of the difficulty of the matter. For it was a matter of great labour and sagacity to choose from such a wide and varied multitude of things those which would be most beneficial for the introduction and the beginning. For that reason I have always loved the wonderful book by Johannes de Sacrobosco which appears to me to have grasped very aptly the first principles of this discipline, and I judge that I have seen in the universities most learned men who preferred this book to others of the same kind with great unanimity, and wanted it to be available in all schools, and to be in everyone's hands. ‘The book that is to live needs to have genius’, says Martial [Epigrams 6.60.10]. But such genius does not fall to the lot of works which do not have the commendation of usefulness. In order for the book to have favourable genius for so many centuries in all schools, among such a variety of opinions, it must be filled with the best things.