A traditional samovar.
The modern samovar is electric, made of excellent quality 18/10 steel. It has a thermostat and capacity of 3/4 of a litre.
Just pour some water in the base, plug it in and turn on the thermostat. When the water is boiled, lower the thermostat at a steady temperature. Fill the teapot with tap water, put in the tea and place it on the samovar to keep it warm.