Of the countless letters written by Michelangelo during a long and arduous career some four hundred and ninety have survived and are known to us in the original autographs, in authenticated copies, or in published versions of letters that are no longer extant. Those contained in the first category are by far the most numerous, and except for a few to be found elsewhere -- mainly in the Florentine State collections, in the Vatican Codex and in the Casa Vasari -- are preserved in two principal archives, the Casa Buonarroti in Florence and the British Museum in London. The manuscripts in the former were acquired by the city, together with the house and the rest of its contents, by bequest in 1858, on the death of Cosimo Buonarroti, Michelangelo's last collateral descendant of the elder branch; those in the latter by the Museum by right of purchase in 1859 from Michelangelo Buonarroti, nephew of the aforesaid Cosimo.
Although selected letters have been quoted, either in whole or in part, by most of Michelangelo's biographers during the past four hundred years, it was not until 1875, when, in commemoration of the quatercentenary of Michelangelo's birth, the Florentine archivist, Gaetano Milanesi, published the text of all, save two of them, that the letters became generally available. Besides assembling the material from the various archives, a service of inestimable value for which all Michelangelo scholars continue to acknowledge their indebtedness, he facilitated their study still further by modernizing the spelling and by supplying the words and letters omitted in the abbreviated forms of the period, while in all other respects providing a faithful transcription of the originals. It is true that few difficulties are presented either by Michelangelo's unusually fair italic hand, or by the shortenings he used, but it would be idle to pretend that the present translation would ever have been undertaken without the use of Milanesi's text, despite the fact that recourse to the autographs in London has nevertheless been constant.
It will be noted that Milanesi's numbering of the letters and mine do not correspond: partly because, whereas he arranged them chronologically in groups, I have arranged them chronologically, regardless of these groups; and partly because he misdated a number of them, in many cases owing to the fact that his copyist in London sometimes failed to provide him with the correct details of the endorsements, upon which much of the accurate dating depends. The extensive researches undertaken since his time have, in addition, enabled us to correct numerous other misdatings. The number which Milanesi assigned to each letter, together with the appropriate information as to the archival source, the place where the letter was written and its known or (if bracketed) . . .