We have a (mostly) home made weighing device. We already had the actual spring scales which weigh up to a lot, but I can't remember how much, probably 50kgs. Two wooden 'A' frames joined at the top with a strong cross pole. Scales suspended from that, then a rope and sling for the sheep attached to the bottom hook of the scales. Our sling was just a polyprop sack, but the whole thing, minus scales, would easily take the weight of a man - we have the pics to show it.
It's all a bit Heath Robinson, but for those of us who are financially challenged, for the occasional weighing of a small lot of meat lambs, it works well.