In Gregory Reed's first appearance, he did use a black magic pentagram on his hand to switch bodies with the real Superman. Interestingly, he couldn't control Superman's super-mass so his heavy body caused his mansion to fall into the ocean. (Act No. 414/1, Jul 1972: "Superman vs. Superstar!")
That story does imply that Superman's kryptonian super-mass is on a par with at least a house. A standard two-story house weighs about 25 tons. I suppose a mansion would be a lot heavier. I'd guess that story implies he's at least 25 tons unless he's controlling his weight (pun unintended).
https://www.supermanthroughtheages.com/wiki/index.php/Gregory_Reed