The key innovation was the creation of what were called the “perpetual endowments” or “inexhaustible treasuries.” Say a lay supporter wished to make a contribution to her local monastery. Rather than offering to provide candles for a specific ritual, or servants to attend to the upkeep of the monastic grounds, she would provide a certain sum of money—or something worth a great deal of money—that would then be loaned out in the name of the monastery, at the accepted 15-percent annual rate.
