If you want to understand yourself, take it and cut off good and bad, long and short, coming and going, high and low, God and Buddha. Cut off all things. You must proceed as if you were walking on thin ice, concentrating totally on each one of your steps. If you make one wrong move you will die and go to hell like an arrow. Passing beyond this realm of not-thinking, you reach the land of true emptiness.
True emptiness is before thinking.
But if you stay there you will become attached to emptiness, and not even the Buddha can save you. When you are hanging by your hands from a mountain ledge, and can let go, not thinking of life or death, then you will have true freedom. You can see the wooden dog eating steel and shitting fire. You make friends with the hairyshelled turtle and the rabbit with horns. You learn to play the flute which has no holes.