Hoo-Ha! Rocks are a great idea - probably straight out of the old books. I'll give them a try when I have the chance. I like the multiple use approach too.My mossgeil swandri...at night fold to shape. Hate carrying very specific single use items. Like an under blanket for the hammock. In real cold just fire my reusable space blanket into the swanny. Simples.
Have tried rolling the hot boulders from the fire under me before but they can be a pain to move about. Does work though.
Hahaha ye I'll bet. And yes, it is out ye olde books. Can't remember what one. You can do a similar thing for lying on the ground. Roll the rocks into a small depression and cover in soil and bracken then your sleep mat over it. It'll stay warm till morning.Just watch were you put your feet if you have climb out in the middle of the night.
Be like like a cat on a hot tin roof