The 4-7-8 breathing technique is based on pranayama breathing exercises. Pranayama is the ancient yogic practice of controlling your breath. These types of mindful breathing exercises have been shown to have many benefits for stress reduction and relaxation. The 4-7-8 breathing technique was developed by Dr. Andrew Weil. He refers to it as a "natural tranquilizer for the nervous system." From WebMD.com (see link)