How long is the timber? 14'or so? That twist in the pic is certainly de-twistable. I once forced a 20' DF 8x8 back to true using the posts it was joined to as levers. The twist was so bad the post at one end was 3' off the deck. Housed joints of course. I would try strapping a long weighted lever to one end, give it a good soaking and let it sit under stress like that for a couple days.
