Among others who exercised themselves in the school of the sculptors Giovanni and Niccola of Pisa, Agostino and Agnolo, sculptors of Siena, of whom we are at present about to write the Life, became very excellent for those times. These, according to what I find, were born from a father and mother of Siena, and their forefathers were architects, seeing that in the year 1190, under the rule of the three Consuls, they brought to perfection the Fontebranda, and afterwards, in the following year, under the same Consulate, the Customs-house of that city and other buildings. And in truth it is clear that very often the seeds of talent germinate in the houses where they have lain for some time, and throw out shoots which afterwards produce greater and better fruits than the first plants had done. Agostino and Agnolo, then, adding great betterment to the manner of Giovanni and Niccola of Pisa, enriched the art with better design and invention, as their works clearly demonstrate. It is said that the aforesaid Giovanni, returning from Naples to Pisa in the year 1284, stayed in Siena in order to make the design and foundation for the facade of the Duomo, wherein are the three principal doors, to the end that it might be all adorned very richly with marbles; and that then Agostino, being no more than fifteen years of age, went to be with him in order to apply himself to sculpture, whereof he had learnt the first principles, being no less inclined to this art than to the matters of architecture. And so, under the teaching of Giovanni, by means of continual study he surpassed all his fellow-disciples in design, grace, and manner, so greatly that it was said by all that he was the right eye of his master. And because, between people who love each other, there is no gift, whether of nature, or of soul, or of fortune, that is mutually desired so much as excellence, which alone makes men great and noble, and what is more, most happy both in this life and in the other, therefore Agostino, seizing this occasion of assistance from Giovanni, drew his brother Agnolo into the same pursuit. Nor was it a great labour for him to do this, seeing that the intercourse of Agnolo with Agostino and with the other sculptors had already, as he saw the honour and profit that they were drawing from such an art, fired his mind with extreme eagerness and desire to apply himself to sculpture; nay, before Agostino had given a thought to this, Agnolo had wrought certain works in secret.