Iron rusts from disuse, stagnant water loses its purity and in cold weather becomes frozen; so does inaction sap the vigors of the mind.
Source: In Pearls of Wisdom, ed. J. Agel and W. Glanze, 1987.
-- Leonardo da Vinci, (Apr 15 1452-1519), Italian painter, sculptor, architect, engineer; He was a renaissance man best remembered for his paintings, Mona Lisa, 1503; The Last Supper, 1498.