吾唯足知 a water basin at Ryoanji Temple, Kyoto
Four Chinese characters, 「吾唯足知 」"ware tada taru wo shiru" are carved on the Tsukubai stone. The feature of the stone is the square water hole in the centre of the stone where the water is stored, forms a part of each letter.
Their literal meaning are " I simply know what is enough".
Or more nicely put,
I am content with what I am (have).
Rich is the person who is content with what he is.
It is a simple design, but very witty, isn't it.