Tradition says that Ruberto Martelli was the earliest of Donatello’s patrons.  So far as we know, there were two Rubertos:  the elder was seventy-three at the time of Donatello’s birth, and must therefore have been a nonagenarian before his patronage could be effectively exercised; the other was twenty-two years younger than the sculptor, whom he could not have helped as a young man.  But there is no question about the interest shown by the family in Donatello’s work.  The David and the St. John, together with a portrait-bust and the coat of arms, still show their practical appreciation of his work and Donatello’s gratitude to the family.  Vasari is the first to mention these works, and it must be remarked that Albertini, who paid great attention to Donatello, mentions nothing but antique sculpture in the Martelli palace.  The David and the St. John Baptist are both in marble, and were probably made between 1415 and 1425.  The David, which was always prized by the family, is shown in the background of Bronzino’s portrait of Ugolino Martelli.[58] It was then standing in the courtyard of the palace, but was taken indoors in 1802 per intemperias.  The statue is not altogether a success.  Its allure is good:  but the anatomy is feminine, the type is soft and yielding; the attitude is not spontaneous; and the head of Goliath, tucked uncomfortable between the feet, is poor.  There is a bronze statuette in Berlin which has been considered a study for this figure, though it is most unlikely that Donatello himself would have taken the trouble to make bronze versions of his preparatory studies.  The work, however, is in all probability by Donatello, and most of the faults in the marble statue being corrected, it may be later than the Martelli figure, from which it also varies in several particulars.  The statuette is full of life and vigour, and the David is a sturdy shepherd-boy who might well engage a lion or a bear.  In one respect the Martelli figure is of great importance.  It is unfinished—­the only unfinished marble we have of the master, and it gives an insight into the methods he employed.  It is fortunate that we have some means of understanding how Donatello gained his ends, although this statue does not show him at his best; indeed it may have been abandoned because it did not reach his expectations.  However, we have nothing else to judge by.  The first criticism suggested by the David is that Donatello betrays the great effort it cost him.  Like the unfinished Faith by Mino da Fiesole,[59] it is laboured and experimental.  They set to work hoping that later stages would enable them to rectify any error or miscalculation, but both found they had gone too far.  The material would permit no such thing, and with all their skill one sees that the blocks of marble did not unfold the statues which lay hidden within.  As hewers of stone, Donatello and Mino cannot compare with Michael Angelo.  Jacopo della Quercia alone had something