Our friend Baquies asked a question that I like very much: my OED Traps Digest has a 10' diameter rolling rock trap, which I basically lifted from Moldvay's Lost City adventure (module B4, area 39), and he probably swiped it from Raiders of the Lost Ark the prior year.
Now, I stipulate that after the boulder comes to a rest, it can be pushed aside 1 in 6 by a normal man. Is that reasonable?
Looking at the Rockhound Resource website, one of the examples in a table there includes a rock that's "Car sized | ~10 ft" weighing in at at about 86,500 pounds (and I double-checked the calculation: assumes about granite density).
An answer to a Quora question (by Charles Collins -- no relation, I assume) says that the optimal coefficient of rolling resistance on level ground is 0.10 (for a car with inflated tires, or a plane bearing). For our rock this gives a critical force of 86,500 × 0.010 = 865 pounds.
Can a man push that much? That's something I suppose a gym could answer. I think it's pretty common to bench press 100 pounds or so. An answer on Reddit here says regarding a leg-press machine, "People can easily hit up to 400-600 pounds or more on these machines, I would design for a force of 1000 pounds to have some safety factor built in."
So maybe we should dial down our rock a little bit, say to about an 8' diameter -- thereby letting it roll a bit more freely down our standard corridor, and also reducing the weight by half, to about 44,300 pounds, with a critical rolling force of about 443 pounds. This seems to put it squarely in the range that a fit man could roll, if he had his back against one wall, and pushed with both legs.
(And our friend Seeker points out that the easiest rock to carve for this purpose would be limestone, so let's say that's the material, which increases the weight a small amount, i.e., by 2% or so.)
What are your thoughts on that? Will it make Sisyphus happy?