Hugh Montgomery cites this story in his God-Kings of Europe (2006:124) and also God-Kings of Outremer (2008:Appendix C).
"Now it came to pass in those days that a Priestess of the Goddess from the village of Bethany of the Tribe of Benjamin and a keeper of the Sacred Doves was affianced to a man called Jeshua for she had served her six years. Now Jeshua was of the House of David the King and they were married.
And Jeshua rebelled against the oppressors against Rome and was defeated, but many Romans were devotees of the Mother and were unwilling to kill her priestess who was with child. So Miriam took ship and was secretly smuggled into Gaul where she was delivered and there she abode many years. Now she bore a daughter who was exceedingly fair and the King of that place looked upon her and demanded that she be his wife but she was promised to the Goddess. But the King would not have it so and took her and made her his wife and she bore him a son and a daughter.
But the Goddess was exceeding wrath for his rape of her daughter and cursed him saying, 'Thy seed shall be estranged from me and thine inheritance taken from thee. Thy seed shall end by the piercing of an eye and so shall thine inheritance cease.
Yet for the sake of my priestess whom thou ravished shall I forgive thee and thy seed if they fulfil those labours which I shall give to them.
They must fight and capture that which was lost to the oppressors of thy wife though they shall not hold it for they shall suffer betrayal (as thou betrayed me). Unless one of thy seed shall end the House of their betrayers by piercing the eye of its Liege. To this family shall I award greatness if they return to me and from this time to that shall be four and one hundred generations.'"
Montgomery states that "the document . . . was around the south of France in various forms at the time of the Albigensian Crusade (1209)." He believes Jacobus de Voragine may have written the Magdalene account in the Golden Legend to refute this one. The English translation is from the 17th century.