The Mind of Leonardo Da Vinci

Leonardo’s thinking was interdisciplinary. When he injected wax into the brain or into the heart to make casts of the inner workings of the body, he was borrowing the “lost wax” technique familiar to sculptors. When he studied friction and invented roller bearings and ball bearings he reasoned that frictional resistance differs according to the nature of the surfaces in contact, and increases in direct proportion to load, and he even estimated (for the first time) a coefficient of friction. But he went further to realize its relevance not just to machines but to the movements of tendons over bones; to the creation of heat by the heart; and to the production of voice by the friction of air on the vocal cords.

Source: blogs.scientificamerican.com