Knight of the Weeping Tree

Re-reading aSoS, the Bran chapter where he goes under the wall, the salty tear reference really stood out. There is a lot of speculation on a thread in this forum about salt repelling the White Walkers. This makes a lot of sense with them being made of ice. It also makes the wall more useful, assuming they can't just go around on the frozen sea. This got me thinking about salt as a poison for White Walkers and other non-humans. This would be the perfect test as part of the Guest Right. If someone eats salt and doesn't die, they aren't a White Walker or other iced based baddy. Therefore, you shouldn't harm them as, compared to the waring between men, the war with the Great Other seems far more important. Also, it might be particularly important not to have a dead guest in your house in the North and beyond the Wall where a dead guest might be even more dangerous than a live one... should they rise again. Finally, we know dragonglass or obsidian comes from dragonstone, with it's many salt and smoke references. Obsidian in reallife is created when lava cools quickly, perhaps when hitting sea water! Wikipedia also lists sodium as an important components. Perhaps, the salt in the obsidian is enough to melt, poison or kill White Walkers!