This article on ways to beat insomnia brought to mind a fail-proof way I discovered many years ago while studying government. (In those days we didn't pretend that politics was a science.)
One of the assigned reading books was a thin volume by Roy C. Macridis that had near-magical powers. A mere three to five minutes with it and I was out. Any time. Any location. Unfortunately, I gave away the book before reaching the age when insomnia strikes. I've half a mind to track it down today.