Corpus of Electronic Texts Edition
The Gaelic Maundeville (Author: John Maundeville)

paragraph 201

And when Magnus Khan conquered the kingdom of Cathay, he himself died, and Sito Khan took his place, and the other two sons went to seek a dominion for themselves, and conquered Prussia and Russia, and called each of them Khan. And hence the king of Cathay is called Magnus Khan, the great Khan, and he says in his own letters that he himself is lord of lords, and king of kings, and he says also that God is king in heaven, and that he himself is king on earth.