Original: The most significant source for the devotion to the Sacred Heart in the form it is known today was Visitandine Saint Margaret Mary Alacoque (1647 â "1690), who claimed to have received visions of Jesus Christ.
Simplified: The most significant source for the devotion to the Sacred Heart in the form it is known today was a nun of the religious congregation of the Visitation of Mary Saint Margaret Mary Alacoque (1647-1690), who claimed to have received visions of Jesus Christ.