there were such "perpetual teapots" in huts in high .bg mountains, basically the hut-keeper boiling a tea of whatever bunch of herbs is next on the shelf, forever (several ~months, some huts were closed for winter). Pick one sprig, add water :)

i have tried few times to achieve the same - or okay, at-least-similar - taste, at home.. but no way. Just hours are not enough :/

Though nowadays, this thing is .. mostly gone.