1 Grosso - John XXIII

John XXIII — born Baldassare Cossa — was declared antipope by the Council of Constance in 1415, the same council that ultimately ended the Western Schism by deposing him alongside two rival claimants and electing Martin V. Coins struck under his authority during the Schism occupy an awkward historiographical position: the Catholic Church long refused to recognize his pontificate, which is why a second John XXIII could be elected in 1958. Cossa was subsequently imprisoned, ransomed by the Medici family, and died in Florence in 1419 — the year Donatello completed his tomb monument.