YouTube star Paul will enjoy a 45lb weight advantage when he takes on the ring legend in Miami on Sunday night.
The 26-year-old looked ripped as he scaled 189.5lb before Mayweather weighed in at a career-high 155lb.
In doing so, Paul avoided a penalty in excess of $100,000 having claimed he would be fined that amount for every pound over 190lb.
And he later claimed he is ready to shock the world and knock out one of the greatest fighters in history.
“He’s not ready, he doesn’t know what to expect,” said Paul. “This is not the biggest fight of my life, this is the biggest fight of his life. He’s got a lot on the line and he’s got everything to lose.
“I’m going to go in there and have fun. The fact I’m even up here proves this s*** is a simulation, none of its real.
“Tomorrow I break the simulation and beat the greatest boxer in the history of the planet.
“I’m going to get it done, it’s a fight and anything can happen. Floyd’s not ready, that’s all I can say.”
Mayweather added: “I’ve been here before so I know what it takes. I’ve fought every different style you can possibly fight
“Height doesn’t win fights, weight doesn’t win fights, fighting wins fights at the end of the day and I can fight. I’ve been at the top for 25 years I know what it takes when its a fight of this magnitude.”
There will be no ringside judges at the Hard Rock Stadium in Miami and no official winner will be announced.
But knockouts will be permitted while the referee will be allowed to stop the fight.
Both fighters will wear professional 10oz gloves after the original rules stated they would pull on 12oz mitts.
And Mayweather has called for even smaller gloves which would increase the likelihood of a knockout even further.
“What I really want are 8-ounce gloves, so we can entertain people,” he said.
“We’re getting closer to what I want, although it’s an exhibition, people want to see blood.”
Mayweather has also downplayed his height and weight disadvantage – and vowed to end the fight by KO.
“Most of the time when I go out there and fight, I’m giving up 20 pounds,” he said. “When I was fighting at 140, the guys I was fighting were going up to 160.
“When I was fighting at 147, guys were going up to 167 within 24 hours. I don’t really worry about the weight. Once again, fighting wins fights.
“I look at it as going out, having a good time, and entertaining the people. I do what I want to do, when I want to do it, and how I want to do it.
“I’m happy that we are able to go out and that someone can get knocked out. When someone can get knocked out, it’s a winner.