A generous tablespoon seems to be roughly the amount needed, but it's always best to use a kitchen scale to make sure you get it exact as possible.
how are you feeling right now? Are you intending to drink the solution, or do you simply want to be closer to considering it? I think it is entirely possible without an anti-emetic, but it would likely be more unpleasant. If you do choose to not use an anti-emetic you should definitely make sure you have mixed two or three glasses of the solution and case of vomiting.
also, if you drink it and you wake up please go to the hospital. This is not the type of thing that you can recover from on your own. you could simply say you Confused it up with normal salt and cooked a meal with it.