This "witness" to the female pope is likely to be based upon Martin's account, and not a possible source for it.
The same is true of Marianus Scotus's Chronicle of the Popes, a text written in the 11th century.
It is claimed that this John was a woman, who as a girl had been led to Athens dressed in the clothes of a man by a certain lover of hers.
According to the Chronicon: John Anglicus, born at Mainz, was Pope for two years, seven months and four days, and died in Rome, after which there was a vacancy in the Papacy of one month.
Other references to the female pope are attributed to earlier writers, though none appears in manuscripts that predate the Chronicon.
The one most commonly cited is Anastasius Bibliothecarius (d.
In the most common accounts, due to her abilities, she rose through the church hierarchy and was eventually elected pope.
Her sex was revealed when she gave birth during a procession, and she died shortly after, either through murder or natural causes.