Plato, Meno

Socrates
Try and tell me how much you would say it is.

Boy
Three feet.

Socrates
Then if it is to be three feet, we shall add on a half to this one, and so make it three feet? For here we have two, and here one more, and so again on that side there are two, and another one; and that makes the figure of which you speak.

Boy
Yes.

Socrates
Now if it be three this way and three that way, the whole space will be thrice three feet, will it not?

Boy
So it seems.

Socrates
And thrice three feet are how many?

Boy
Nine.

Socrates
And how many feet was that double one to be?

Boy
Eight.

Socrates
So we fail to get our eight-foot figure from this three-foot line.

Boy
Yes, indeed.

Socrates
But from what line shall we get it? Try and tell us exactly;