On March 22, 1508, at the end of what is considered Leonardo's second stay in Florence prior to his second sojourn in Milan, he still lived «in the house of Piero di Braccio Martelli» (previously mentioned by Leonardo around 1503) together with the sculptor Giovan Francesco Rustici, whom he assisted in sculpting three bronze statues to adorn the outside of the Baptistery (the Preaching of St . John). Here he began to compile a part of the Codex Arundel: «Begun in Florence in the home of Piero di Baccio Martelli on the day of March 22, 1508. And this is a collection without order taken from many papers, which I have copied here, hoping then to put them in order in their proper places, according to the matters of which they treat; and I believe that before I come to the end of this endeavour, I will have repeated the same thing several times; so that, Reader, do not criticize me, because the things are many and memory cannot retain them well enough to say: this I will not write, because I have already written it. And if I wished to avoid such an error, I would always have to read everything already written, in every case that I wanted to copy, so as not to repeat it, resulting in long intervals of time between each of the writing sessions».
At present the fourteenth-century Via degli Spadai is called Via Martelli. The residence of Piero di Braccio Martelli was encapsulated in the Scolopi boarding school (up to 1775 a Jesuit monastery), when it was enlarged in 1836. On the façade is a stone tablet commemorating Leonardo's presence here.