Sister Caterina Capitani, an Italian nun who belonged to the Congregation of the Daughters of Charity, suffered from numerous critical illnesses during the 1960s. In May 1962, she developed the abdominal inflammation peritonitis.

As papal biographer Renzo Allegri tells the story in St. Anthony Messenger magazine, one of Capitani's fellow nuns brought her a relic of Pope John XXIII, a piece of the sheet on which he had died, and placed it on her abdomen.

She prayed to John - not to cure her, because she thought it was too late for that, Allegri writes, but to take her to heaven.

She fell asleep and is said to have then felt a hand pressing on her abdomen, which she assumed to be her doctor's. But when she opened her eyes, she saw Pope John standing beside her bed, according to Allegri's report, smiling and holding his hand on her wound. The pope is said to have told her she was healed and to call the other sisters into her room.

She thought she had been dreaming, Allegri writes, but the wound on her abdomen had disappeared, and she was hungry. She went on to live a normal, healthy, productive life.

Although two miracles are normally needed for sainthood, Pope Francis let this one suffice for John XXIII, citing the holy life that he lived.