Well now, that's an interesting question. (Although, as a chemist, I do have to wonder about who would *need* a supersaturated solution of Sodium tert-Butoxide).
For starters, a super saturated solution is only metastable - the slightest disruption of the system, and the material will precipitate out until saturation is re-established.
It's not only water that you need to worry about, any protic solvent will react with it.
The next question is: what do you need to do with it? That will frequently determine which solvent you need to put it in.
A nice generic solution, of course, would be tert-butyl alchohol - since that's what it's made from....
Doctor9
