Testing a sunstone in Oregon fog
The sagas mention a sólarsteinn, a sunstone, that could show where the sun was on an overcast day. Plenty of researchers now think it was Iceland spar, clear calcite, which splits light in two and can help you locate the sun through cloud if you know what you're doing.
As a blacksmith I love things that actually do something. So I bought a chunk of Iceland spar and took it out on the grayest morning this week. Looked through it at the sky, rotated it slowly until the two faint spots evened out, and marked the direction.
Checked it against my phone compass and the sun's position: off by maybe ten degrees. My ancestors crossed the North Atlantic with tools like this. I can barely cross my driveway. Hail to the navigators.