If anyone is interested in the historical development of these practices (as Gates mentioned), they are known (in Latin) as ars memoria. They were extremely common in ancient Greece, but (ostensibly) came under attack the the development of writing (Plato complained bitterly about it). They were revivified in the Renaissance, and were connected to a whole host of linguistic studies, including the development of "universal" or "artificial" languages, and, interestingly, cryptography.