To put in into the context, here is the complete passage:
Inside You is Nothing, Nothing at All
In my third year as a monk, I had doubts about the nature of samadhi and wisdom. Really desiring to experience samadhi, I strove ceaselessly in my practice. As I sat in meditation, I would try to figure out the process, and therefore my mind was especially distracted. When I did nothing in particular and was not meditating, I was fine. But when I determined to concentrate my mind, it would become extremely agitated.
"What's going on?" I wondered. "Why should it be like this?" After a while, I realized that concentration is like breathing. If you determine to force your breaths to be deep or shallow, fast or slow, breathing becomes difficult. But when you are just walking along, not aware of your inhalation and exhalation, breathing is natural and smooth. In the same way, any attempt to force yourself to become tranquil is just an expression of attachment and desire and will prevent your attention from settling down.
As time went by, I continued to practice with great faith and growing understanding. Gradually I began to see the natural process of meditation. Since my desires were clearly an obstacle, I practiced more openly, investigating the elements of mind as they occurred. I sat and watched, sat and watched, over and over again.
One day, much later in my practice, I was walking in meditation sometime after 11pm. My thoughts were almost absent. I was staying at a forest monastery and could hear a festival going on in the village in the distance. After I became tired from walking meditation, I went to my hut. As I sat down, I felt that I could not get into the cross-legged posture fast enough. My mind naturally wanted to enter into deep concentration. It just happened on its own. I thought to myself, "Why is it like this?" When I sat, I was truly tranquil; my mind was firm and concentrated. Not that I did not hear the sound of singing coming from the village, but I could make myself not hear it as well.
With the mind one-pointed, when I turned it toward sounds, I heard; when I did not, it was quiet. If sounds came, I would look at the one who was aware, who was separate from sounds, and contemplate, "If this isn't it, what else could it be?" I could see my mind and its object standing apart, like this bowl and kettle here. The mind and the sounds were not connected at all. I kept examining in this way, and then I understood. I saw what held subject and object together, and when the connection was broken, true peace emerged.
On that occasion, my mind was not interested in anything else. If I were to have stopped practicing, I could have done so at my ease. When a monk stops practicing, he is supposed to consider: "Am I lazy? Am I tired? Am I restless?" No, there was no laziness or tiredness or restlessness in my mind, only completeness and sufficiency in every way.
When I stopped for a rest, it was only the sitting that stopped. My mind remained the same, unmoved. As I lay down, at that moment my mind was tranquil as before. As my head hit the pillow, there was a turning inward in the mind. I did not know where it was turning, but it turned within, like an electric current being switched on, and my body exploded with loud noises. The awareness was as refined as seemed possible. Passing that point, the mind went in further. Inside was nothing, nothing at all; nothing went in there, nothing could reach. The awareness stopped inside for awhile and then came out. Not that I made it come out-no, I was merely an observer, the one who was aware.
When I came out of this condition, I returned to my normal state of mind, and the question arose, "What was that?" The answer came, 'These things are just what they are; there's no need to doubt them:' Just this much said, and my mind could accept.
After it had stopped for awhile, the mind turned inward again. I did not turn it, it turned itself. When it had gone in, it reached its limit as before. This second time, my body broke into fine pieces, and the mind went further in, silent, unreachable. When it had gone in and stayed for as long as it wished, it came out again, and I returned to normal. During this time, the mind was self-acting. I did not try to make it come and go in any particular way. I only made myself aware and observed. I did not doubt. I just continued to sit and contemplate.
The third time the mind went in, the whole world broke apart: the earth, grass, trees, mountains, people, all was just space. Nothing was left. When the mind had gone in and abided as it wished, had stayed for as long as it could, the mind withdrew, and returned to normal. I do not know how it abided; such things are difficult to see and to speak about. There is nothing to compare it with.
Of these three instances, who could say what had occurred? Who could know? What could I call it? What I have spoken about here is all a matter of the nature of mind. It is not necessary to speak of the categories of mental factors and consciousness. With strong faith I went about practice, ready to stake my life, and when I emerged from this experience the whole world had changed. All knowledge and understanding had been transformed. Someone seeing me might have thought I was mad. In fact, a person without strong mindfulness might well have gone mad, because nothing in the world was as before. But it was really just I who had changed, and yet still I was the same person. When everyone would be thinking one way, I would be thinking another; when they would speak one way, I would speak another. I was no longer running with the rest of humankind.
When my mind reached the peak of its power, it was basically a matter of mental energy, of the energy of concentration. On the occasion I just described, the experience was based on the energy of samadhi. When samadhi reaches this level, vipassana flows effortlessly.
If you practice like this, you do not have to search very far. Friend, why don't you give it a try?
There is a boat you can take to the other shore. Why not jump in? Or do you prefer the ooze and the slime? I could paddle away any time, but I am waiting for you.