The Five Forms of Rapture
1. Minor rapture (khuddaka piti): Your hair stands on end, and tears come to your eyes, either with or without your being aware of the fact. This happens, not through a sense of sadness, but through a feeling of pleasure, fullness, and satisfaction in a skillful object.
2. Momentary rapture (khanika piti): A shiver runs through the body, and a feeling of satisfaction appears for a flash in the heart, like a flash of lightning or the flicker of lightning bugs.
3. Recurrent rapture (okkantika piti): A stronger sense of thrill comes over the body, like waves washing over a shore.
4. Transporting rapture (ubbega piti): A sense of transporting joy comes welling up through the body to the point where you lose control and start acting or speaking in various ways. For instance, sitting in concentration, you may suddenly raise your hands in adoration or bow down. If the feeling grows really strong, you may not be conscious of what you're doing. You may start speaking, the words coming out on their own without any forethought on your part.
5. Pervading rapture (pharana piti): A flush or tingling sensation spreads through and permeates the body. Sometimes the body itself appears to grow and swell, or else to become very small.
When any one of these forms of rapture arises, you should keep your powers of reference firm. Don't give in to the feeling and don't let it take over. Keep your mind unaffected. Don't lose your sense of your body and mind. Keep your words and actions firmly under control. Don't act under the influence of the feeling. If the sense of rapture comes in a gentle form, well and good; but if it comes in a strong form, and you give in to its power, you can easily get hooked and start jumping to false conclusions. Don't go assuming that you've gained this or reached that, because all of these feelings are inconstant, stressful, and not-self. If you get fixated on them, the mind won't be able to attain proper concentration of any worth or value. If you fall for them, they'll become enemies of your concentration and discernment.