Here's a photo I took 24 year ago on Colonsay. It shows A' Clach Thogalaich, the stone of lifting, which lies near the road at the north end of the golf course (at least it did in 1993). The boulder weighed in at around 250 pounds. I was not in the mood to rupture anything, so I didn't try to lift it.
See this Old Man of the Stones page for some interesting descriptions of attempts, some successful, to lift the Colonsay stone. If you're in the mood to test your strength, and can't make it out to Colonsay, there are also some lifting stones on North Uist described in the same link.