Prophetistan

How common would it be to claim prophethood in the premodern world? Incredibly common. Al Biruni, an 11th-century polymath, describes an interesting case of someone attempting to mix Zoroastrianism and Islam, including features of each to appeal to both sides: 

Bahafirid b. Mahfurudhin

-Thereupon in the days of 'Abû-Muslim, the founder of the 'Abbaside dynasty, came forward a man called Bahafirid ben Mahfurûdhin in Khwaf, one of the districts of Nîshâpûr, in a place called Sîrâwand, being a native of Zûzan. In the beginning of his career he disappeared and betook himself to China for seven years. Then he returned, and brought with him among other Chinese curiosities a green shirt which, when folded up, could be held in the grasp of a human hand; so thin and flexible was it. He went up to a temple during the night, and when he thence descended in the morning, he was observed by a peasant who was ploughing part of his field. This man he told that he had been in heaven during his absence from them, that heaven and hell had been shown unto him, that God had inspired him, had dressed him in that shirt, and had sent him down upon earth in that same hour. The peasant believed his words, and told people that he had witnessed him descending from heaven. So he found many adherents among the Magians, when he came forward as a prophet and preached his knew doctrine.

He differed from the Magians in most rites, but he believed in Zarâdusht, and claimed for his followers all the institutes of Zarâdusht. He maintained that he secretly received divine revelations, and he established seven prayers for his followers, one in praise of the one God, one relating to the creation of heaven and earth, one relating to the creation of the animals and to their nourishment, one relating to death, one relating to the resurrection and last judgment, one relating to those in heaven and hell and what is prepared for them, and one in praise of the people of paradise.

He composed for them a book in Persian. He ordered them to worship the substance of the sun, kneeling on one knee, and in praying always to turn towards the sun wherever he might be, to let their hair and locks grow, to give up the Zamzama at dinner, not to sacrifice small cattle except they be already decrepit, not to drink wine, not to eat the flesh of animals that have died a sudden death as not having been killed according to prescription, not to marry their mothers, daugh-ters, sisters, nieces, not to exceed the sum of four hundred dirhams as dowry. Further, he ordered them to keep roads and bridges in good condition by means of the seventh part of their property and of the revenue of their labour.

When 'Abû-Muslim came to Nîshâpûr, the Maubadhs and Herbadhs assembled before him telling him that this man had infected Islâm as well as their own religion. So he sent 'Abdallah b. Shu'ba to fetch him. He caught him in the mountains of Badaghîs and brought him before 'Abû-Muslim, who put him to death, and all his followers of whom he could get hold.

His followers, called the Bahâfirîdiyya, keep still the institutes of their founder and strongly oppose the Zamzamís among the Magians. They maintain that the servant of their prophet had told them that the prophet had ascended into heaven on a common dark-brown horse, and that he will again come down to them in the same way as he ascended and will take vengeance on his enemies.