I was reading a book about historical supernatural stuff in Mexico and the author details a ritual which was allegedly used to gain a type of guardian spirit called a nagual (note that this word is used for many supernatural things). It was taken from a colonial source listed as General History by Herrera dating from 1530 though I haven't been able to find it online with a quick web search.
"The Devil deluded them, appearing in the shape of a lion, or a tiger, or a coyote, a beast like a wolf, or in the shape of an alligator, a snake, or a bird, which they called naguales, signifying keepers or guardians, and when the bird died the Indian who was in league with him died also, which often happened and was looked upon as infallible. The manner of contracting this alliance was thus: the Indian repaired to the river, wood, hill, or most obscure place, where he called upon devils by such names as he thought fit, talked to the rivers, rocks or woods, said he went to weep that he might have the same his predecessors had, carrying a cock or dog to sacrifice. In that melancholy fit he fell asleep, and either in a dream or waking saw one of the aforesaid birds or other creatures, whom he entreated to grant him profit in salt, cacao, or any other commodity, drawing blood from his own tongue, ears, and other parts of his body, making his contract at the same time with the said creature, the which, in either a dream or waking, told him, 'Such a day you shall go abroad a-sporting, and I will be the first bird or other animal you shall meet, and will be your nagual and companion at all times.' Whereupon such friendship was contracted between them that when one of them died the other did not survive, and they fancied that he who had no nagual could not be rich."
