When my mother was a child (Northeast US), they'd take baked potatoes to bed to keep their feet warm. Growing up we had one of the soft/red hot water "bottles" and it was used mostly when someone was in pain or sick.
One side of my family were farmers in prior generations (mid-Atlantic US). They utilized heated bricks in the same way that you're describing the potatoes.
Yeah, my mom (grew up in the rural south US) has told me multiple times about how her mom would heat bricks fro the beds each evening. They were very poor and had no central heat so wood stove, bricks, and multiple kids to a bed (there were 13 of them) was the go to winter strategy.
They also double as a midnight snack
My mom said they'd bring them to school the next day for lunch.