Gliese 581-G (Just for fun)

[Nexis]

That's exactly what I was saying like, five or something posts back, lol... not about Vikings, but a sun dial on a plate that's sitting on water. I wonder if there's a way it could be made to fit on a person's wrist if the craftsmanship was advanced enough. Like in a glass bauble or disk. It would need to be oil in that case so it wouldn't evaporate and fog the glass.

Hmmm. How about using mercury? Far more stable than water. Maybe the plate could be magnetic and point to North to mark your bearings, then read the shadow length.
I think a wrist version would be too small for serious navigation. You would need a much larger plate to get an accurate distance reading.
For that I would think loose gimbals on a tripod would keep the plate level while a floating compass on mercury will give you a bearing to adjust the plate to read the shadow. The plate would be engraved as accurately as the technology of the people will allow.
It would be large, maybe 1 foot across to be accurate. This would be used by explorers, merchants and the military. Casual travelers usually would stay on known paths and not go very far from home so the use of a personal compass would be more of a rich man's toy or jewelry.

Edit: Wait a min! I keep forgetting about spirit levels! You don't need to float it. Just place a bubble in a fluid in the center of the compass and you can adjust it till it becomes level.