With the prefecture of Giovanni Battista Audiffredi (1714-1794) the Casanatense reached its maximum splendor, acquiring that universality of content that characterized its collections until the mid-19th century. He was born in Saorge (Nice) on February 2, 1714 and was given the name of Giulio Cesare, which he changed to Giovanni Battista when he entered the Dominican Order in 1730, attached to the Convent of S. Maria a Formello in Naples. After completing his studies at the school of illustrious masters, he taught as a Lector in various convents of the Dominican Province of Lombardy. In 1749 he obtained a degree in Magisterium in sacred disciplines and in the same year the curators of the Casanatense Library in Rome elected him librarian. Ten years later he became Prefect.
A man of great intelligence, Audiffredi embodies the figure of the librarian as described in the entry in the Encyclopédie. A contemporary, E.Q. Visconti, wrote about him in 1785: “In every kind of news and particularly bibliographical, Father Audiffredi, the first librarian of the Casanatense, stands out. Well versed in literature and science, he is perhaps the most encyclopedic man we have in Rome. A skilled astronomer, a learned antiquarian, a good naturalist, an excellent bibliophile, he has written with praise in these different genres and recently published a small work on the Roman editions of the 15th century, full of beautiful news and observations”.
Equipped with a keen bibliographic criterion and a boundless culture, he organizes and administers the library considering it not as a field to be exploited to his own advantage, but as an institution whose bibliographic resources must be made available to scholars, through rich and well-ordered catalogues. His intense bibliographic activity is in fact summarized by the Audiffredi Catalogue of all the books owned at that time by the Casanatense, which is still in use today, representing, for a part of the historical Casantense funds, the only cataloguing support.
Audiffredi, an astronomer, was commissioned by the Duke of Sermoneta to build a sundial in the Caetani Palace, where an observatory was established that he used for several years. He was also a collector of ancient medals, archaeological finds, seals, and scientific instruments, which he collected in a small museum in the Casanatense Library. He died at the age of 80 on July 4, 1794.