We have it really easy. We want a softdrink, we can just walk into the nearest newsagent and buy one. But the Brazilian natives like a nice drink too. But they have to work a little harder for it. They pick guaraná berries, grind them with a pestle and mortar, make them into a fat cigar shape and smoke it for days until they turn into a solid stick which is easy to store for a long time.
So now you have the ingredient how would you grind them into a drink? Well... they fish this massive river fish, called Pirarucu. They remove the tongue, which is mostly made of bone, place it on an ant hill for a couple of weeks so they remove all the flesh from it, and dry it for another couple of weeks. After all that it turns into a very efficient grinder, which they use to grind the solid stick of guaraná.
Check out this video I found at a fellow chef's site - Alberto Landgraf. It's in Portuguese but it's quite self explanatory.