I don't know where this fascination with supremely big and heavy and very expensive prime lenses will end but...
The RF 50 f1.2 weighs over 2 lbs, is 3.5 inches fat and 4.5 inches long, and costs $2,300. It has a 77mm front filter element.
The RF 85 f1.2 weighs close to 3 lbs, is over 4 inches fat and close to 5 inches long. It takes an 82mm front filter. It has a theoretical entrance pupil diameter of 71mm.
An RF 135 f1.4 would need a theoretical entrance pupil of 96mm. That makes the front element nearly twice as massive as the 85mm f1.2. So you are probably looking at a lens that weighs 5 lbs, is 5.5 inches fat, 6.5 inches long, takes a 105mm front filter and costs $3,799.