MikeSol: As for how I did it, as I mentioned already, I kept letting Nate the Snake flee. Nate is considered non-evil by the game. This required a lot of cure poison spells, not only because of Nate's poison attack but because getting through Magincia (where Nate is located) requires you to pass over at least one swamp tile. Your method is the way to do it.
You could probably get away without that much cure poison spells. Remember, if you are already poisoned, any further poison effects will have no further effect.
Therefore, if you just keep healing yourself (with spells or by resting outside (but note that resting has a cooldown)), you will not need to keep curing your poison only to get re-infected. (Yes, poison does not hurt you while you are resting.)
By the way, being poisoned will prevent enemies from putting you to sleep.
(Note that none of this post applies to the NES version.)
