Among the bibliographical treasures exhibited in the cases in the Escorial Library is No. 13, a exceptionally fine book of hours which belonged to Charles V. This book is not just another one of the countless books of hours produced in the later Middle Ages and the Renaissance to assist the laity in their devotions, but a work specially produced for the occasion of Charles I of Spain's voyage by sea in 1520 from Spain to Germany, where he was to be crowned Holy Roman Emperor.
The work comprises 37 folios on vellum, measuring 270 x 180 mm., written in solemn Gothic script, and the italic style known as bastard. It contains only three of the canonical hours: matins, for the departure from the port of Corunna, vespers, to pray for a safe journey and compline, as preparation for building the house of God.
The author of the book was the renowned Roberto César (Robert de Keysere) of Ghent, whose life and work in the first few years of the 16th century are well documented. His mastery of classical languages was sufficient for him to be appointed to a chair at the Three Languages College at Tournai University. Some of his correspondence with Erasmus has survived.
This codex is especially remarkable for its 12 masterly Flemish miniatures, most of which portray the Emperor; the most outstanding is the Apotheosis of Charles V. But there are also portrayals of biblical figures (a Solomon sitting in judgment and a Moses among others) and also the ships which were to carry the Spanish king, such as that appearing on folio 1, showing St James unfurling the sails, St. Nicholas at the tiller with St. Livinus, the patron saint of Flanders, as passenger.
Modern critics attribute these important miniatures to a sister of Robert de Keysere's named Clara, whose devotion to painting is attested.
The book pleased the Emperor to such an extent that he kept it in his own library and we know from archives that he ordered the author to be given a recompense of the considerable sum of sixty pounds.