I didn't yawn once during Clare Elizabeth Dea 's Embodied Writing workshop.  This was with 3 hours sleep and after listening to 15 minutes of 1.5 Hz delta and 40 Hz gamma tones on YouTube to rest and revitalise me. I looked for this on https://blog.bulletproof.com/sleep-hacking-awesome-high-performance-day-after-2-5-hours-of-sleep/