Masonry stoves are heating stoves developed in medieval Europe, or even earlier. Some sources are mentioning some kind of similar Roman stoves.
It is a wood burning stove with high efficiency and high thermal mass. Because of that mass it can accumulate heat in the fireplace and the result is a great efficiency because most of the wood gases are burnt. It is an efficient ecological alternative to ordinary wood burning stoves.
Useful links: [1] Demotech simple brick stove
http://www.dataphone.se/~ncteknik/We_are_setting_up_a_Swedish_ceramic_stove.html Swedish ceramic stove aka kachelofen (German name)
http://mha-net.org/ the best site on the internet about masonry stoves