John K Jordan
I found this in a walnut 8/4 board today. A walnut nut evidently fell into a crevice in a walnut tree and the tree grew around it. It looked a little more like a nut before I ran it through the planer but I didn't think to take a picture of it then.
I've had this and some other boards from the same tree for maybe 30 years and this was the first time I looked at it closely!
The nut looked like it was past it's prime.