Well when I go to Pembs. in September will bring back a bluestone in the boot of the car...
I have'nt seen much raft building for water by the stonengineers, perhaps that should be there next experiment..... making stones float on water.
Let's face it, given enough time and manpower practically anything can be moved anywhere overland - the same cannot be said about sea crossings (though I hasten to add that I'm not saying they didn't or couldn't do it :-)