SergioUK wrote:Not exactly mummification but for a feeling of being trapped up close to someone, a one-piece waterproof suit can be a lot of fun.
Along these lines, another idea that might be worth trying would be a surfboard bag. Many of them are probably quite big enough for two people to get into together, and would certainly force the two to remain intimately together. At least some bags are strongly built enough that you would have no chance of being able to break out, so you would be really trapped. As with many things, you get the quality you pay for.
I think the two people might fit in better with one person's head by the other's feet, whereas I imagine they would probably prefer to be oriented the same way - but some bags would probably accommodate this - although the weight or build of the occupants would be crucial to this.
One thing that could potentially cause problems is overheating; so this would be best done either on cold days or perhaps only for a shortish time. If you don't have a third person to lock you both in, it is quite possible to do this from inside, using a combination padlock - if the bag doesn't have padlock loops, you can simulate these by using cable ties on the zipper pulls.
The gap between the zippers should allow enough air to get inside if your mouth is close to that gap; but if the head-to-feet arrangement is used, I'm not sure how it would be for the person whose face is not near that opening. Try it without actually locking it, and see if it works before committing to it.