OK - we were chatting a little about this in our October board -- but I am not sure what crib mattress to get!

I can't find any solid info online really, I know I want something firm, and possibly organic/natural - but that's it!

Tell me what you got & why.

And, we have the Babyletto Mercer crib which takes a 52"L x 27.5"W mattress up to 6" thick.