Capitalization of knowledge happens when knowledge generates an economic added value. The generation of economic value can be said to be direct when one sells the knowledge for some financial, material or behavioral good. The generation of economic value is considered indirect when it allows the production of some material or service goods that are sold on the market. The direct mode comprises the sale of personal know-how, such as in the case of a plumber or of a sports instructor. It also comprises the sale of intellectual property as in the case of patents, copyrights or teaching. The indirect mode comprises the ways with which organizational, declarative and procedural knowledge is embodied in goods or services. The economic return in both cases can be financial (for example cash), material (for example the exchange of consumer goods) or behavioral (for example the exchange of personal services). In ancient times, the direct and indirect capitalization of knowledge was based mainly on procedural knowledge. Artisans, craftsmen, doctors, and engineers sold their know-how in direct or indirect ways within a market or outside of it. Up to the first industrial revolution, the knowledge that could be capitalized remained mainly procedural. Few were the inventors that sold their designs and blueprints for the construction of military or civil machines and mechanisms. There were some exceptions, as in the case of Leonardo da Vinci and several of his inventions, but, since technological knowledge remained essentially tacit, it drove a capitalization based primarily on the direct collaboration and involvement of the inventors in the construction of machines and in the direct training of apprentices.