I grew up in a big house that was a generation behind when it came to heat. We used wood and coal to heat the water that cycled through the radiator system. The floors were cold when we got up in the mornings and the radiators took time to warm up.
The radiators were multipurpose and functional. On wash day the heaviest clothes were spread there to dry, or when snow-pants and mittens came in wet from playing in the snow there was no better spot to let them dry. They were a towel heater at bath time and a place to warm your clothes in the morning. After a day outside in the cold it was perfect to take a seat on the radiator until your buns got too hot. The radiators were better than a fireplace.
The furnace didn't produce heat until you "fixed" the fire. In my high school years I learned to produce a fire starting with some newspapers or trash, then adding some kindling, then big logs or chunks of coal. The coal burned hot! Once the fire was going nicely the water would begin to boil and run through the pipes to the radiators. You'd hear the hissing and creaking as the heat moved through the house and before long the house began to warm up nicely. However if you were upstairs waiting for the heat it seemed like an eternity before the room became comfortable. I'd sit on the downstairs radiator and imagine it was getting warm until it finally did.
I miss warming my hands on the angles of the radiators. I'm surprised I'm not permanently dented by the years of sitting on the bumpy warmers. Daddy usually "fixed" the fire and really got things heated up. Often during family dinners it was much too warm and mama would have to open the door to the porch to cool it down enough to be comfortable. Daddy loved to be warm and I think I got my internal temperature from him.
"The fire on the altar must be kept burning; it must not go out. Every morning the priest is to add firewood and arrange the burnt offering on the fire and burn the fat of the fellowship offerings on it. The fire must be kept burning on the altar continuously; it must not go out" (Leviticus 6:12-13 NIV).
Unfortunately the fire in our furnace would usually go out overnight, making for those cold mornings. But we were thankful to have the heat again when the fire got going.