Parri Spinelli was most important painter from Arezzo in the early 1300s. About 30 of his drawings are extant, more than for any other artist of the period, when drawing was just beginning to be common to artistic practice. Spinelli used a quill pen and ink on a large sheet of paper to copy the composition of a monumental mosaic by the Florentine artist Giotto that adorned the portico of Old Saint Peter’s Basilica in Rome (since destroyed). In this scene from the Bible, Christ walks on water at right, while Saint Peter kneels before him in front of a ship filled with Christ’s disciples. Spinelli focused on the outlines of the figures, using a limited vocabulary of parallel and perpendicular lines to suggest shallow depth and shadow. Paper was rarely wasted. On the other side of the sheet (1961.38.b), Spinelli continued the copy, rendering two large ships and two rowing boats full of people.The drawing formed part of a model or pattern book that Spinelli would have kept in his studio. The book was broken up, probably as early as the 1500s, and two other drawings with the same subject—in the Metropolitan Museum of Art, New York, and in the Musée Bonnat in Bayonne—are known.