At the same time Guglielmo made the round window for the facade of the Church of S. Francesco, a great work, in which he represented the Pope in Consistory, with the Conclave of Cardinals, and S. Francis going to Rome for the confirmation of his Rule and bearing the roses of January. In this work he proved what a master of composition he was, so that it may be said with truth that he was born for that profession; nor may any craftsman ever think to equal him in beauty, in abundance of figures, or in grace. There are innumerable windows executed by him throughout that city, all most beautiful, such as the great round window in the Madonna delle Lacrime, containing the Assumption of Our Lady and the Apostles, and a very beautiful window with an Annunciation; a round window with the Marriage of the Virgin, and another containing a S. Jerome executed for the Spadari, and likewise three other windows below, in various parts of the church; with a most beautiful round window with the Nativity of Christ in the Church of S. Girolamo, and another in S. Rocco. He sent some, also, to various places, such as Castiglione del Lago, and one to Florence for Lodovico Capponi, to be set up in S. Felicita, where there is the panel by Jacopo da Pontormo, a most excellent painter, and the chapel adorned by him with mural paintings in oils and in fresco and with panel-pictures; which window came into the hands of the Frati Ingesuati in Florence, who worked at that craft, and they took it all to pieces in order to learn how it was made, removing many pieces as specimens and replacing them with new ones, so that in the end they made quite a different window. He also conceived the wish to paint in oils, and for the Chapel of the Conception in S. Francesco at Arezzo he executed a panel-picture wherein are some vestments very well painted, and many heads most lifelike, and so beautiful that he was honoured thereby ever afterwards, seeing that this was the first work that he had ever done in oils.