I, Mark Twain being of sound mind, have spent everything

Age is an issue of mind over matter. If you don't mind, it doesn't matter.

I have a prodigious quantity of mind; it takes me as much as a week sometimes to make it up.

I must have a prodigious amount of mind; it takes me as much as a week, sometimes, to make it up!

No man has a wholly undiseased mind; in one way or another all men are mad

When I am king they shall not have bread and shelter only, but also teachings out of books, for a full belly is little worth where the mind is starved.