I just rest for 12 hours in the InnIt does seem like wyverns are dropping fewer emeralds. Not sure if it's just a luck thing?
For clarity, how are you re-freshing the map? Staying at an inn, time lapsing?
Its very likely that you get emeralds at Mercian Royal Crypt. Everytime I go there, theres always emerald (the big one). In my opinion, it is much better to farm here if you are strong ennpugh to clear the crypt on your own