The Book of Rites
As ruling over all, under the sky, (the king) is called “The son of Heaven.” …His death is announced in the words, “The king by (the grace of) Heaven has fallen.” In calling back (his spirit), they say, “Return, O son of Heaven.” When announcement is made (to all the states) of the mourning for him, it is said, “The king by (the grace of) Heaven has gone far on high.” When his place is given to him in the ancestral temple, and his spirit-tablet is set up, he is styled on it, “the god.” The son of Heaven, while he has not left off his mourning, calls himself, “I, the little child.” While alive, he is so styled; and if he die (during that time), he continues to be so designated.
– from The Book of Rites.
The Book of Rites (also known as the Liji) is a compendium of texts adopted from the philosophers of the Warring States (the two schools of Chinese philosophy which differ on whether man is by nature good or evil), and is considered part of the core Confucian canon. The date of composition for The Book of Rites is uncertain. It includes important definitions for court ceremonies and detailed information about the life and teaching of Confucius.