But still, cool at night.
A friend knowing that I make felted wool quilts that look similar sent me this link:
https://okanarts.com/blogs/blog/hot-water-bottle
I tried one, liked it so much I gave them out for Christmas!
Some were the Japanese ones as shown and some antique copper ones from ebay most of them for less than $25 delivered but need polishing. A grode one for $14 delivered!
Fill from a teapot or set directly on a gas burner, with LID OFF.
They stay HOT all night long, using a thermocouple and remote meter... Starting at 9PM @ 190 F. degrees @7AM 127 F.
The next morning!!! THEN PUT IT AT MY FEET THE NEXT MORNING WHILE CHECKING FR.
And all of them were used the last couple of nights!!!