I would like to research this method in historical texts, but any search on google for ‘body scan’ only returns results related to the modern vipassana movement.
Kayagata-sati Sutta. Buddha was explicit that breathing is part of the body, so anapanasati is a sub-set of body scanning.
"Kayanupassana" comming under "Chathu Satipatthana". You can find detailed discription in "Maha Satipatthana Sutta"
Also refer and search for "Anapanasati Meditation".