David Combs wrote:

I recall from a thermodynaics course eons ago that whatever the materials,
the amount of heat energy flowing from one to the other, per second,
is 100% *proportional* to the temperature *difference* between the two.

I'm afraid you recall wrong, for radiation.

...an 80-degree (F) block of steel would be able to transfer enough heat
to you (r butt) to keep you toasty comfortable...

It would cool your butt, compared to a pillow.

Nick