A storm glass looks a little like this. According to old lore (which I won't give you the history of, but it boils down to the fact that farmers couldn't afford mercury barometers to measure air pressure, so they came up with something else), they can predict weather.
How? By mixing one up, keeping it in one place, and then watching for the following changes:
If the liquid in the glass is clear, the weather will be bright and clear. If the liquid is cloudy, the weather will be cloudy as well, perhaps with precipitation. If there are small dots in the liquid, humid or foggy weather can be expected. A cloudy glass with small stars indicates thunderstorms. If the liquid contains small stars on sunny winter days, then snow is coming. If there are large flakes throughout the liquid, it will be overcast in temperate seasons or snowy in the winter. If there are crystals at the bottom, this indicates frost. If there are threads near the top, it will be windy.
Sadly, I have done some research and there is absolutely no evidence that this device has better weather predicting accuracy than your best guess, or, than tossing a coin in your pocket might have. Less than 50%, in most situations, with actual results ranging from 38 to 62 percent.
Now, even if they can't 100% predict weather, I still thick they have their merit, and they might just work for you! Perhaps they work better in some locations than others. The only way to find out is to try it! So, use this video to make your very own storm class, and find out if you can predict the weather this way. At the very least, you'll have some pretty crystals to look at. Or, try making a romantic necklace version for that special someone. Or, one you can wear around your neck, hang up in camp, and hope it helps you predict the weather!