As load increases on a sled you merely increase the length and width of the runners. So long as the pounds per square inch doesn't melt all the snow under them or it's it's too cold for the pressure to melt the surface of the snow a sled has virtually zero friction. Since virtually all the work associated with moving stones horizontally is caused by friction there is very little work required to drag them all the way across the country. They'd only lose efficiency dragging stones down hills so steep they couldn't keep up with them and dragging them down hills with no uphill afterward. It would be easy enough to recruit local people as the stone moved and it could just sit during the summer. It's no like anyone's gonna take it.

Anything a caveman could do is not rocket science.

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Man fears the pyramid, time fears man.