Vincenzo Viviani (1622-1703) wrote the Racconto istorico della vita di Galileo [Historical account of the life of Galileo] in the form of a letter to Prince Leopold de' Medici (1617-1675). Dated April 29, 1654, it remained unpublished during the author's lifetime; it first appeared in print in 1717, in the Fasti Consolari of the Florentine Academy. Viviani claims to have explained the events of Galileo's (1564-1642) life "recorded with historical integrity and complete honesty, having extracted most of them from the words of Galileo himself and from the reading of his works, from his lectures and conversations with his disciples, from the testimony of his intimates and relatives, from public and private writings, from various letters of his friends, and, lastly, having corroborated and compared them with other evidence [...]." The book contains a long description of the role played by Galileo's son, Vincenzo (1606-1649), in the studies on the application of the pendulum to the clock.