Wool is the warmest blanket material, especially wool from animals who live in cold terrains. Wool is a natural material that includes a crimp, which helps to hold in more heat than a material with an open weave. It also provides natural insulation.
The softest organic towels I’ve found are Temesecal Towels from Coyuchi.
This is the best rechargeable 16340 battery I could find:
The best 21700 Rechargeable Li-ion batteries are: