Progressive Relaxation is a common relaxation technique that involves what’s often called a Body Scan.
You can find variations in numerous places. I’ve found useful descriptions of Progressive Relaxation in the following books:
by Jon Kabat-Zinn, Ph.D.
Chapter 5 is called Being in Your Body: The Body-Scan Technique
by Rick Hanson, Ph.D. with Richard Mendius, MD
There’s a good, simple summary on pages 81-82.
by Alan Konell, M.S.W.
Appendix 1 is a transcript of self-hypnosis, which includes progressive relaxation