According to the Book of History (Shujing), Shun before passing the throne over to the Great Yu spoke thusly:
'(According to the rules for) the regulation of divination, one should first make up his mind, and afterwards refer (his judgment) to the great tortoise-shell. My mind (in this matter) was determined in the first place; I consulted and deliberated with all (my ministers and people), and they were of one accord with me. The spirits signified their assent, and the tortoise-shell and divining stalks concurred. Divination, when fortunate, should not be repeated.' [The counsels of the Great Yu - James Legge]
If this part of the record is correct and not because of accretion, Yi diviners can learn a thing or two on divination from the ancients. Yi scholars may learn something too. Go figure.