Yoga Nidrā is a 30 minute guided meditation done lying down in shavāsana. It can bring about a profound state of relaxation, utilizing techniques such as rotation of consciousness through the parts of the body, breath awareness, invoking various bodily feelings and sensations, and invoking vivid or archetypal images with the imaginative faculty. Once memorized, you can do this practice without the recording, as long as you don’t have to think about it; so a lot of repetition is needed to reach that point. There are minor variations in yoga-nidrā; so if you get bored of this recording, try another one.