When we inhale, the air comes into the inner world. When we exhale, the air goes out to the outer world. The inner world is limitless, and the outer world is also limitless. We say "inner world" or "outer world", but actually there is just one whole world. In this limitless world, our throat is like a swinging door. The air comes in and goes out like someone passing through a swinging door.
When your mind is pure and calm enough to follow this movement, there is nothing: no "I", no world, no mind nor body; just a swinging door.
-- from Zen Mind, Beginner's Mind by Shunryu Suzuki p. 29
