Kettlebells are thought by many people to be uniquely Russian. While there is no question that they have very strong roots there, kettlebells have a long tradition in other areas of the world as well. This rare picture was taken in Iran, circa 1897, showing these practitioners of 'Vaezesh-e Pahlavani' (Iranian Martial Arts) who obviously use them as a part of their training. The text offers no explanation as to why they are fastened together by ropes.
Also of note are the Kaebade (i.e. Iron Bows) at their feet. That unique training tool is swung from one shoulder to the other, building upper-body strength.