“Perseverance is the hard work you do after you get tired of doing the hard work you already did.”

“As Blake wrote in The Marriage of Heaven and Hell: You never know what is enough unless you know what is more than enough.”

“It is too difficult to think nobly when one thinks only of earning a living.”

“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettie...”

“To know the history of science is to recognize the mortality of any claim to universal truth. ”

“The scientist only imposes two things, namely truth and sincerity, imposes them upon himself and upon other scientists.”