To arrive at this knowledge needs thorough work. There is no guaranteeing that you will gain such knowledge at one sitting. Perhaps one in a million will. In the days of the Buddha there are people who attained to the Path and Fruit after listening to a stanza. But you can't expect such things today. It was then the Buddha himself who was teaching. He knew the disposition of his listeners very well. The listeners on their part were people of perfections. But today the preacher is just an ordinary person who preaches what little he has learnt. He does not know the disposition of his listeners. It will be difficult to say that the listeners are men and women of perfections. If they had been, they would have gained deliverance in the days of the Buddha. So we cannot guarantee you will gain special knowledge at one sitting. We can only tell you that you can if you work hard enough.
How long do we have to work? Understanding impermanence, suffering and not self begins with the investigating knowledge. But it does not come at once. It is preceded by purity of mind, purity of views, and purity of transcending doubts. To speak from the level of the present day meditators, a specially gifted person can achieve this knowledge in two or three days. Most will take five, six, or seven days. But they must work assiduously. Those who get slack at work may not gain it even after fifteen or twenty days have passed. So I will talk about working in earnest in the beginning.
Insight meditation is incessant work - meditate whenever you see, hear, smell, taste, touch or think, without missing any thing. But to beginners, to note everything is quite impossible. Begin with several. It is easy to observe the moving form in the rising and falling of the abdomen. We have already spoken about it. Note without a let up rising, falling, rising, falling. As your mindfulness and concentration grow stronger, add the sitting and the touching and note, rising, falling, sitting, touching. As you note on, ideas may come up. Note them, too: thinking, planning, knowing. They are hindrances. Unless you are rid of them, you have not got purity of mind and will not have a clear understanding of mind-matter phenomena. So, don't let them in. Note them and get rid of them.
If unbearable feelings like tiredness, hotness, pain, or itch, appear in the body, concentrate on them and note: tired, tired or hot, hot as they arise. If the desire arises to stretch or bend the limbs, note it too, 'desire to bend, desire to stretch.' When you bend or stretch, every move should be noted: bending, bending, stretching, stretching. In the same way, when you rise, note every move. When you walk, note every step. When you sit down, note it. If you lie down, note it too.
Every bodily movement made, every thought that arises, every feeling that comes up, all must be noted. If there is nothing in particular to note, go on noting rising, falling, sitting, touching. You must note while eating or having a bath. If there are things you see or hear particularly, note them too. Except for the four five six hours you sleep, you keep noting things. You must try to be able to note at least one thing in a second.
If you keep on noting thus in earnest, you will, in two or three days, find your mindfulness and concentration quite strong. If not in two or three days, than in five or six. Then very rarely do want on thoughts come up. If they do, you are able to note them the moment they come. And they pass away the moment you notice them. The object noted like the rising and falling and the mind noting it seem to be well timed. You note with ease. These are signs that your mindfulness and concentration have become strong. In other words, you have developed purity of mind.