You have three points of contact with the bike -- bar, pedals, saddle. Between the three, 100% of your weight is divided (unevenly). I've read that 50-60% of your weight is routinely carried on the saddle, about 30% on the pedals, and the rest on the bar. I can't link to that, since I don't remember where I read it, so all I have to go on is my admittedly imperfect memory.