I was just reading some of the older messages regarding having more than one circuit splice in a single junction box.
There is obviously the potential for someone to be injured if they believe only one circuit is involved.
I have a couple of junction boxes where I've got more than a single circuit spliced. I've solved the problem for myself (Poor memory after a few years) by using a self adhesive plastic label holder. The kind found in office supply stores for use on binders.
They're 1" by 3 1/2" and I just list the 2 circuit breakers involved and stick it on the junction box.
These will remain in place forever and a day and I'm not concerned about the next guy to work on that box. Including myself when I've forgotten why I installed the box to begin with. :)
e.g.
2 circuits in box Breaker #'s 4 & 5 (Tie barred) and # 26