Inscribed within plaque of design, at lower center, in pen and brown ink, "S. IOANES / PROTECT ["or" in superscript above T].
Denison, Cara, Myra Nan Rosenfeld, and Stephanie Wiles. Exploring Rome : Piranesi and His Contemporaries. New York : Pierpont Morgan Library; Montréal : Centre Canadien d'Architecture, 1993, no. 33, repr.
This drawing shows Piranesi's design for the stucco decorating the vault above the church's nave. It is rich with symbols of the Knights of Malta, featuring St. John the Baptist (the knights are formally the Order of St. John) as well as references to the order's maritime and military history. Although long identified as Piranesi's own study, it is not in his hand and must instead be a copy by a studio assistant--probably a clean copy of the master's drawing supplied to the stuccatore Tommaso Righi, who executed the stucco vault decoration.
Morgan, Jane Norton, 1868-1925, former owner.
Morgan, Junius Spencer, 1892-1960, former owner.
Morgan, Henry S. (Henry Sturgis), 1900-1982, former owner.