How to get weight over the back under hard braking I've just been doing some hill repeats and killing the boredom I got thinking, what is the best position to be in when braking hard (emergency stop, coming downhill etc.)? Obviously you want to keep the back wheel from lifting off the ground. 

For example, I could lean over the handlebars (stupid but its illustrative) sit in the middle of the saddle, sit on the back of the saddle, or hang off the back beyond the saddle...

What is the most effective way to transfer weight on to the back wheel?

(On a road bike)
Hang your buttocks off the back of the saddle is the only appropriate answer. 

You can see great evidence of this in cyclocross races when racers go from climbing to steep descents (in some cases) and go straight to the drops and hang their rear end off the back of the bike. 

Here is a downhill rider doing an extreme example of exactly this: