In Robert Fitzgerald's translation of The Odyssey, the door to Polyphêmos' cave is described as a "great boulder." While a specific weight is not given for the boulder, this translation does claim that, "Two dozen four-wheeled wagons, with heaving wagon teams, could not have stirred the tonnage of that rock from where he wedged it over the doorsill." Though 'tonnage' may not be a literal translation of how much the boulder weighs, the details Homer provides confirm that this is an incredibly heavy boulder--we can assume that the combination of 'tonnage' and the example of wagons and wagon teams means this boulder weighs more than a ton.
Homer discusses the weight of the boulder further, calling it "his great door slab" and saying that Polyphêmos has no trouble moving it. Odysseus knows that he and his men cannot move the slab on their own, and while Homer doesn't give us exact figures for how many accompany Odysseus to the island, Homer writes, "As luck would have it, the men I would have chosen won the toss--four strong men, and I made five as captain." That means that the boulder is heavy enough that Odysseus' men, who number over five, can't move it even if they try all together.
This is why Odysseus has to trick Polyphêmos into letting him and his men out. The cyclops is so strong that he can move this boulder on his own, making him a formidable enemy, and as long as the slab is in place they cannot escape. This is a problem of brains, not brawn, which is where Odysseus excels--they escape the cavern by tricking the cyclops rather than through brute strength.
Homer does not provide an exact weight for Polyphemus's cave door (actually a large boulder). Odysseus describes the door as:
- “a tremendous, massive slab -- no twenty-two wagons, rugged and four-wheeled, could budge the boulder off the ground” [Fagles translation]
- “no twenty-two of the best four-wheeled wagons could have taken that weight off the ground and carried it” [Lattimore translation]
- “so huge that two and twenty strong four-wheeled waggons would not be enough to draw it from its place against the doorway” [Butler translation]
(Note that the singular form is Cyclops and the plural form is Cyclopes.)