“Only those who will risk going too far can possibly find out how far one can go.”
“Never measure the height of a mountain, until you have reached the top. Then you will see how low it was.”
“The greatest challenge to any thinker is stating the problem in a way that will allow a solution.”
“But thou liest in thy throat; that is not the matter I challenge thee for.”
“An I thought he had been valiant and so cunning in fence, I'ld have seen him damned ere I'ld have challenged him.”
Quotes via Wikiquote (CC BY-SA), each with its original source.