Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind. Leonardo da Vinci's Notebooks edited by Edward McCurdy

More from Leonardo da Vinci

• You cannot leave everything to Fate, boy. She's got a lot to do. Sometimes you must give her a hand.
• 640K ought to be enough for anybody.
• 640K ought to be enough for anybody. 1981
• A baby is God's opinion that life should go on.
• A bank is a place where they lend you an umbrella in fair weather and ask for it back when it begins to rain.
• Absence makes the heart grow fonder: Isle of Beauty, fare thee well!