Is it possible to not make the weight in a boxing match, if you are too light?

The whole rule about making weight is that you can't exceed (be over) a certain weight. There is no rule about being under that weight. That is why Floyd Mayweather fought Oscar De La Hoya at a 154lbs maximum, but Floyd weighed only 150lbs, the most he has ever weighed for a fight but not 154 like Oscar.