Some friends & I,tried transpiration bags some many yrs. ago,Out in Mojave/Death Valley area,with very Poor results.We also made solar stills,& they showed some promise,Had we found some plants with a bit more moisture,1 of 4 of us, would probably be able to survive,for a time anyhow.I remember drinking more than a Qt. of water,Digging my hole for the still!None of us had pee'd in the holes either,which would have increased our gathered amounts of water.I recall we totaled around a 1/2 Pt.of water,the next morning!The Transpiration bags had enough in each,to Possibly get your lips wet,If That!It had gotten Windy overnight,& It was Hot at 2AM,So that was a Big Factor!