When to ask Admissions about formal letter?

[jwf]

I got a call from a professor on Friday from UC Berkeley (Top Choice!) but I was working at the time in the freezer room and it was hard to actually have a conversation. He basically congratulated me and told me to anticipate an email about visit weekend, soon^TM. When should I email the department asking about the formal acceptance letter? I figured 1-2 business days?

[TakeruK]

First of all, the formal acceptance letter often comes from the Graduate School, not the department. This formal letter usually comes much later. An informal but official letter will likely come from the department soon, but the call told you to anticipate an email for the visit weekend, which can come before they are ready to send any sort of official acceptance letters (formal or informal). 

I would say give it a week before following up. Unless there is a rush to get the details for some reason (i.e. you're trying to book another visit or the call said that the visit is happening really soon, i.e. in January).