Performers often get goose pimples all over their bodies and it can be referred to as rapture. There are different forms of rapture though, some are subtle while others are more energizing.
One form of rapture that often arises in meditation is the sensation of mental energy rushing through the body. It feels like a wind or wave is passing through you. Lightness is another form of rapture, perhaps better described as a sense of levitation.
Rapture can arise during any meditation posture. So, what triggers it? Rapture arises when the mind takes a delightful interest in the meditation object, or put in other words, it's triggered when the meditation object excites the mind.
Rapture Is Often Called Piti
In my early days as a meditator, I often experienced piti while practicing Tibetan Chenrezig meditation. And since I didn't have a meditation teacher at the time, my experiences confused me a great deal. I used to believe that these pleasant waves of mental energy meant that I had achieved a higher level of Chenrezig practice - which had nothing to do with it.
Rapture or if you like to call it piti, is simply a sign that the mind is becoming focused and delights in the meditation object.
In the next question-and-answer post, I will take a look at the many benefits of rapture in meditation.
Best of luck!