No, soaking and weighting it down to flatten it won't work. Sorry.

Okay ... thanks Jon for your reply.

Sure -- sorry I didn't have better news. If you intend to use the table indoors and want it flat, it would probably be easiest to simply make a new top for it. If it will be outdoors and exposed to the weather, I wouldn't spend a lot of time fussing over it because the weather will undo your hard work anyhow.

I usually tell people trying to unwarp a board is like trying to unring a bell.

The link below explains what's happened and suggests a possible cure.

Here is a link that might be useful: compression shrinkage

Thanks for the reply and for the link, bob's nephew. I read the whole thing. I guess we'll give up on the idea. It sounded plausible, but I guess not.

Jon, the table will be a covered patio and will end up having my small garden tools, gloves, seeds and stuff like that on it so I think I will just go ahead and sand, stain, varnish, and pretend the curves add to the charm. :-)

Thanks again to you both. It saved us a lot of time and trouble trying to straighten it.