Suppose a man who was not blind beheld the many bubbles on the Ganges as they drove along, and he watched them and carefully examined them; then after he had carefully examined them they would appear to him empty, unreal and unsubstantial. In exactly the same way does the monk behold all the corporeal phenomena, feelings, perceptions, mental formations, and states of consciousness-whether they be of the past, or the present, or the future, far or near. And he watches them, and examines them carefully; and, after carefully examining them, they appear to him empty, void and without a Self.

(Buddha Sakyamuni)