My 2 cents - either leave at 1 month or after 6 ... anything in between just smack of indecision or incompetance. While I agree with Carang, I think there are some jobs that you just know, within 5 minutes of starting, that are not for you. IN that case, better to get out quick before the employer starts relying on you, wasting money training you etc etc. If you 're not going to quit fast, then stick it out for at least 6 months to give them some value for hiring/visa/training etc.
And ask better questions about what the job entails next time.
PS - my record for scaring off a new employee is 3 hours.....