I think self-knowledge is the rarest trait in a human being.

- Elizabeth Edwards

Happiness in intelligent people is the rarest thing I know.

- Ernest Hemingway

One of the rarest things that a man ever does, is to do the best he can.

- Josh Billings

The strongest are those who renounce their own times and become a living part of those yet to come. The strongest and the rarest.

- Milovan Djilas

An absolutely new idea is one of the rarest things known to man.

- Thomas More