I meant a cap on the Essence itself, not the weapon. I've not seen any stat boosted by more than +3 on the Essence. So I was curious if its possible to get higher, or +3 to each.
I have gotten a couple of +4's. The chances of successful etching goes down the higher it is though, at low rank it's pretty easy, so you don't save that much by getting a +3/+4.