Spoleto. There has been much speculation as to whether Botticelli spent a shorter period of time in another workshop, such as that of the Pollaiuolo brothers or Andrea del Verrocchio. However, although both artists had a strong impact on the young Botticelli's development, the young artist's presence in their workshops cannot be definitively proven. Lippi died in 1469. Botticelli must have had his own workshop by then, and in June of that year he was commissioned a panel of Fortitude (Florence, Galleria degli Uffizi) to accompany a set of all Seven Virtues commissioned one year earlier from Piero del Pollaiuolo. Botticelli's panel adopts the format and composition of Piero's but features a more elegant and naturally posed figure and includes an array of "fanciful enrichments so as to show up Piero's poverty of ornamental invention." In 1472 Botticelli took on his first apprentice, the young Filippino Lippi, son of his master. Botticelli and Filippino's works from these years, including many Madonna and Child paintings, are often difficult to distinguish from one another. The two also routinely collaborated, as in the panels from a dismantled pair of cassoni, now divided between the Louvre, the National Gallery of Canada, the Musée Condé in Chantilly and the Galleria Pallavicini in Rome. Key early paintings Botticelli's earliest surviving altarpiece is a large sacra conversazione of about 1470–72, now in the Uffizi. The painting shows Botticelli's early mastery of composition, with eight figures arranged with an "easy naturalness in a closed architectural setting". Another work from this period is the Saint Sebastian in Berlin, painted in 1474 for a pier in Santa Maria Maggiore, Florence. This work was painted soon after the Pollaiuolo brothers' much larger altarpiece of the same saint (London, National Gallery). Though Botticelli's saint is very similar in pose to that by the Pollaiuolo, he is also calmer and more poised. The almost nude body is very carefully drawn and anatomically precise, reflecting the young artist's close study of the human body. The delicate winter landscape, referring to the saint's feast-day in January, is inspired by contemporary Early Netherlandish painting, widely-appreciated in Florentine circles. At the start of 1474 Botticelli was asked by the authorities in Pisa to join the work frescoing the Camposanto, a large prestigious project mostly being done by Benozzo Gozzoli, who spent nearly twenty years on it. Various payments up to September are recorded, but no work survives,