There's an old rumor, or perhaps myth, about the only woman ever to have become Pope. I don't think I have to go into detail about how the Church felt long ago toward women especially if one was an elected official which just didn't happen. Whether or not the story happens to be true, I'll offer you some clues. Maybe you can do you own investigating and find details which I may have missed. I'd love to know your findings.
The story states that John Anglicus was unanimously elected Pope in 853 AD after Pope Leo IV passed away. As Pope John VIII she ruled for two years until one day while riding from St. Peter's to the palace of St. John Lateran, the Pope stopped by the side of the road and gave birth to a baby boy. John wasn't really John after all. He was a woman disguised as a man. This happened in 855 AD.
There two stories about her fate. Some people believed that her feet were bound together and she was dragged by horse while people (fellow Catholics) pelted her with rocks. Others believe that she was sent to a convent to repent for her sins.
In my opinion I don't think the story of Joan is true. The first mention of her is in the thirteenth century. I find it odd that, if the story were true, historians would make no mention of her until more than three hundred years after the incident which surely would have shocked the Catholic world to this very day. It's possible that there was a cover-up. This wouldn't be the first time the Church tried to cover its tracks and keep the truth from the faithful. Pope Leo IV died July 17th 855 AD according to official records and Pope Benedict III immediately took the Papacy.
Pope John VIII did exist and reigned for ten years between 872-882 AD but I can't find any evidence that he was really a woman disguised as a man. Keep in mind that the Protestant were enemies of the Church at the time. Pope Joan may have been propaganda. They would use the myth of Joan against the Church, even trying to prove that she existed and I can imagine that they may have made up much of her fable to prove a point. It's my conclusion that Pope Joan didn't exist beyond fable, however, her legend was immortalize in the tarot as the High Priestess.