Unless it’s a real light bowl, I’ll oftentimes keep it in the box and bring it in strapped to the hand cart. Slower, but don’t want to tweak my back again.
The hand cart has what is essentially a rubber fan belt just above each of the wheels that contacts the stair treads and rolls on bearings. Helps to glide the load over each stair tread smoothly, rather than drag/scrape.
Used to install a lot of Gerber Viper and Avalanche toilets, and even in the elongated and ADA compliant height that’s a pretty light weight bowl.
My wholesalers lost access to those toilets in 1.6 gpf, so I eventually switched to American Standard Champion 4 in 1.6 gpf. Great toilet, but heavy.
Before leaving the Gerber name I did continue to install them for a while with aftermarket flush valves tuned to 1.6 gpf. But putting a $25 aftermarket flush valve into a brand new Avalanche gets expensive. Since Gerber wouldn’t give me what I want, American Standard seems like a natural progression.