Naked Sitting - Yikes

"Turn your head to the wall my darlings, while the gentlemen trot by. " [vague memory of "beyond the fringe" with Dudley Moore, Peter Cook, et. al.]

So I was on a biz trip last week. Brought my zafu and got some good sitting done. Not as much as at home, but much more than the last trip I took. There was a handy configuration of mirrors in the sink area, so I decided to give my zazen posture a look-see. And, blush, blush, I did this au-natural. Thankfully the mirror did not break, and I was able to identify a big mistake in my sitting.

What I had thought was a straight spine, was really over-doing it. The above picture sort of demonstrates the same issue in a standing position. The left image is "natural" the right is forced. I have been pushing my chest out, and pooching my butt too far back. My posture looked sway-back. When I relaxed just a bit, to what felt on the inside like the beginning of a slouch, my back looked normal. It also turns out that the sway-back posture I had was exposing my left leg artery/nerve (?) to more constriction. With a more natural posture, my leg stays way more awake (I'm a half-lotus'er)

So I recommend at least one session of nude sitting with mirrors to everyone who has a habitual leg sleeping, or back strain after a while. Try different things like puffing out your chest, tilting your hips forward and back. See what actually straightens your spine and how it may differ from what feels like a straighter spine. Calibrate your sense to a the position of a natural relaxed, but still straight and upright spine. The "middle way" of sitting.