4 days
Self control mostly. I was taught to meditate by doing nothing but sitting, eyes closed, counting my breaths. It gave me a strong control over my thoughts. Now if I want to sleep, I lie down and turn my brain off. I’m out in a few minutes if it’s not too hot.
In my experience in the US it’s interchangeable. Typically palm out is used to convey more cheerfully or for emphasis, while palm in is more casual or less emphatic.