This is kind of funny. I was just pulling a head and it was wedged with... red cedar. Lol. Anyone who stumbles upon this thread in the future, don't do that. That's an example of way too soft. At least it was easy to pull!
I'll also add that it's my belief that if you're gonna use a harder wood it's advisable to spend a little extra time getting the taper right. One of the things I like about poplar is that there's not much worry in this regard, it compresses a good deal. Harder wood wedges, I have found, are best thinner than their soft counterparts. If they aren't you can drive them in what may seem to be enough, but they don't seat as far down and are more apt to spit out.
This may be self evident, but on the other hand I just pulled a cedar wedge...
As an aside, I had one axe come that did not have a sawn kerf. The tongue was actually split (more like a riven kerf) just a bit, and there was one small, narrow, non-stepped metal wedge. The split was no more than 2" deep. I should mention the tongue was carved absolutely perfectly. It was an old axe and the hang was actually rock solid. I think it had been an old timer who also dunked his axe in motor oil, every void in the eye was filled with crud that suggested as much.
ETA: I want to clarify that it was not me who wedged with cedar, it was that way when it came to me.