When there was no electricity during the pre-electrification era, a device was used in India, to heat the bathing water. This water heating device is called Bumbo in Gujarat.
There is a whole pipe (copper) in the center which is filled with hot coal, the water is then added around it in the vessel. The hot coal will heat up the water.
I have converted this Bumbo into an original floor lamp.
Check out this video of the Bumbo water heater in function, you’ll better understand the use of this object: