Man is most nearly himself when he achieves the seriousness of a child at play. – Heraclitus

There are children playing in the streets who could solve some of my top problems in physics, because they have modes of sensory perception that I lost long ago. – J. Robert Oppenheimer

Never neglect an opportunity to play leap-frog; it is the best of all games, and, unlike the terribly serious and conscientious pastimes of modern youth, will never become professionalized. – Herbert Beerbohm Tree, as quoted by Hesketh Pearson (“Sir Herbert Tree,” Modern