One of the Yoga postures, called Savarasana, is completely different from the others and has its own particular effects. I describe it as the dead-weight pose but that is not quite the literal translation.
This is not a movement but a state of being. Wearing loose clothing, lie flat on your back on a comfortable surface (e.g., a rug, a mattress, even a grassy lawn), arms at your sides, legs slightly apart. Your eyes may be open or closed (I prefer keeping them open). There should be an awareness that your head, body, arms, and legs are all in contact with and supported by that surface. Imagine that the surface you are lying on is gently rising up, like a mythical flying carpet, and that gravity is pulling you flat against it. You, in short, are to become a dead weight, without any muscle tension in your head or limbs.
While movement is not part of this asana, breathing certainly is. You take the usual long slow breaths, feeling the air massage your forehead, feeling your rib cage slowly expand and contract. And you simultaneously focus on relaxing. Recall, that for any asana, muscles not in use are to be relaxed. Since none of your muscles are required for this asana, you seek to relax all of them. Between the long, slow breaths and the total relaxation you are, in effect, putting your body into the condition of deep sleep.