In quoting the foregoing particulars of the early sale of MSS. and of the cost of production, no attempt has been made to calculate the present value of the amounts set down, because the data for such a calculation are not available. It will, however, be well if the reader remembers that the various amounts mentioned must have been equal at the very least to ten times these sums in the present day. Professor Middleton multiplies by ten, but when we find an expert scribe charging one penny and twopence for one leaf, and the “commons” of another is set down at tenpence per week, we may safely reckon the multiplier at considerably more than ten in the fourteenth and fifteenth centuries. The scribes and illuminators already mentioned were the individual workers, who were employed by corporations and men of wealth to produce books for their libraries; but the wholesale producers of books, who employed armies of scribes, must not be overlooked in this place. Vespasiano di Bisticci of Florence (_b._ 1421) was the chief of these booksellers, and he assisted to form the three most famous libraries in Italy--the Laurentian in Florence, that of the Vatican, and the library of Federigo, Duke of Urbino, which was afterwards bought by Pope Alexander VII. and incorporated into the Vatican Library. Vespasiano was an author as well as a bookseller, and has recorded some of his doings in his _Vite degli Uomini Illustri_. He gives a detailed list of the works he obtained for the Duke of Urbino, which comprised all the known classics, the Fathers, books on astrology, science, medicine, art, music, and all the Italian authors and poets. Vespasiano claimed that in this magnificent library, which cost 30,000 ducats, every author was found complete, and not a page of his writings was missing. Every book was written on vellum, and there was not a single one of which he was ashamed. Vespasiano was ever ready to form a library, as the following anecdote will prove.