“For Henry gives the details of peculiar worship paid to the Great Turtle, and the oracles received from this extraordinary Apollo of the Indian Delphos.”
Inferred Fuller names 'Henry' as the source for details of Great Turtle worship at Mackinaw. Alexander Henry the Elder's Travels and Adventures in Canada and the Indian Territories (1809) is the canonical fur-trade memoir that covers Fort Michilimackinac (1760s) and includes accounts of Ojibway religious practices including the Great Turtle oracle.