A Yashica TLR heavy? Not unless your comparison is a P&S digisnapper or a 110 or Minox or something.
Mine is lighter than most of my 35mm cameras by the time I add the zoom I'm normally using on the latter, and in an entirely different league from my Mamiya 645Pro with its AE prism and winder grip, while shooting a bigger negative. (Of course, with fixed lens, not interchangeable backs, rudimentary meter at best etc. TANSTAAFL.)
One of the things I like so much about the Yachica is that it's so easy to carry around and use.