Baldassare Cossa

1370 - Antipope John XXIII, antipope of the Pisan party was born as Baldassare Cossa in Procida, Italy.

1408 - He was one of the seven cardinals who, in May, deserted Pope Gregory XII, and, with those belonging to the obedience of Antipope Benedict XIII, convened the Council of Pisa, of which he became the leader.