Saint Andrew is identified by his attributes of a cross and a book. The cross refers to his martyrdom by crucifixion. The Saint Andrew panel was originally part of the upper right tier of a large altarpiece commissioned by a wealthy public officer for a church in Pisa. St. Andrew's haunting gaze in this painting is turned toward Christ on the cross, shown in the altarpiece's upper middle panel. Other panels of the fifteen-foot-tall altarpiece are in museums throughout Europe. The modulation of light and shadow in Saint Andrew's robe gives the illusion of physical weight and solidity to the figure underneath. Masaccio was famous for his innovative depiction of three-dimensional forms in painting and his ability to portray figures with convincing physical and emotional presence.