Reference wanted for "To see your past karma, look at your present body (and environment)...."
Found it... mostly -- 
Tweet by H.H. The Dalai Lama, May 6, 2010...


  If you wonder what you were doing in the past, look at your body; to know what will happen to you in the future, look at your mind.


3149 retweets -- so that's probably where I saw it. As for adding environment to body, that's probably my interpolation, since the material circumstances of one's present life are clearly karmic, according to Buddhadharma.

It's probably impossible to trace this to a single origin, however, as it seems to be all over the place in various versions, including from sources other than Buddhists.