The law of contiguity comprises many features. Everything which comes into close contact with a person—clothes, footprints, the imprint of the body on grass or in bed, the bed, the chair, everyday objects of use, toys and other things—all is likened to different parts of his body. There is no need for the contact to be permanent or frequent. A road, objects touched by mere accident, bath water, a fruit that has been bitten into, and so on—all can be used magically. Magic performed over residues of meals—which is practiced throughout the world—follows from the idea that there is a continuity and complete identity between the remains, the food consumed, and the one who has eaten—the latter being substantially identical to the food partaken by him.

From Marcel Mauss’ A General Theory of Magic, translated by Robert Brain, London: Routledge, 1972 (first published in 1902), p. 80.