So where's the catch (weight)?

Wasn't The Mayweather v Marquez fight supposed to be at a catchweight of 144 pounds? So how come Mayweather weighed in at 146 pounds? Apparently, he'll have to pay a $600,000 penalty for not even attempting to get down to the contract weight. But that's scant consollation for Marquez, who was duly pummelled by a man possibly a stone (or more) heavier at the start of the contest. Don't get me wrong, Mayweather is an unbelievable fighter - but, boy, does he like to play things safe.