What is the meaning of this unusual tombstone?


Boing Boing reader Travis emailed me this photo, along with the following:

I found this odd tombstone in Walla Walla, Washington. I liked getting high and strolling through the graveyard cuz there were a lot of really old masonic tombs. But this is just….the weirdest one I've ever seen. Maybe I missed something and someone on boingboing might have a clue?

UPDATE: More photos here. There are inscriptions on the back and on top of the tombstone.