Constancy does not begin, but is that which perseveres. - Leonardo da Vinci

We do not lack devices for measuring these miserable days of ours, in which it should be our pleasure that they be not frittered away without leaving behind any memory of ourselves in the mind of men.

Learning is the only thing the mind never exhausts, never fears, and never regrets.

Those who fall in love with practice without science are like a sailor who enters a ship without a helm or a compass, and who never can be certain whither he is going.