At the University of Paris, during the era when paper was very expensive,(around 1000 AD) they taught a memory system. When you start, you visualize your personal space, at first the size of a kitchen drawer. You visualize the things you learn as material objects that you place in the drawer. As your space fills up, you replace it with larger storage areas. After the drawer fills up, you replace it with a cupboard, then a wardrobe, then a walk in closet. At the end, your personal space is the size of Notre Dame Cathedral, with all you have learned sitting in the pews.
It parallels what you achieve with weight training.