In his book 'Going to Extremes', Joe McGinniss describes being left in an unheated shack and having to get through the Alaskan night unprepared.
He found a candle, and sat in a chair with the candle in a can, beneath the chair, then he wrapped himself and the chair in a blanket or something.
A candle in a can between your crossed legs, as you lean against a tree with your poncho over everything, to capture the heat, can get you through a night, of course a candle lantern with a 9 hour candle is smaller and easier to carry.
Now I’m not sure it was his book where I learned about the candle, and chair idea.
Not that it matters much, the concept is something to remember.
I make a point of keeping a few glass-encased votive candles in the house. You occasionally see them cheap in dollar stores. They burn for up to 6 days.