Tianfei is a religious and cultural reference in Book One (Awake to Emptiness) in The Years of Rice and Salt.

Tianfei is the ancient Chinese goddess of the sea. The Tianfei palace is located in Taicang, China where Zheng He prayed for peace and good fortune before departing for his voyages.

More information along with a picture of Tianfei can be found at this website.

References
Robinson references Tianfei on pg.40 in Book One where we see the Chinese sailors, including Zheng He, praying to Tianfei to calm the waters so they can return safely to China from their voyage. Robinson references Tianfei so the audience can understand the religious, spiritual, and cultural context of China at the time, thus better understanding their culture and the influence it would have on the rest of the world if Robinson's alternative history had occurred.