The jewel-temple of farthest China

The Temple of the Jewel is a round temple at the far end of the land of China, with seven doors. Inside it is a great dome, and at its top is something like a jewel that lights up the regions of the temple. So al-Mas'udi describes it. ²

He reports that kings tried to take it, but no one could come within ten cubits of it. In it is a well with a seven-sided mouth, and on its collar, in the Musnad script, is written what connects to a store of books and the history of the world. ²

This is al-Mas'udi's account alone, and it needs an additional source.