Salt is in insomnia.

 A hard to say, when are first time used salt. But with salt cured headaches, teeth, ascites, gout, lungs etc. My father is war endured, that on the war, he shares, towels wetted in strong salted infusion used to cure pus wounds. And for the normal vital activity a human within a day need to use on 10 gr salt is a not full teaspoon.

And in insomnia before half hours till sleep take warm shower, rub with terry towel, and wear, keeping legs naked. Add on the basin bottom a salt, stand on her, and stay on her shifting from one leg to other for 6 min, and keeping stepping on place a thin trickle add hot water, that feet covering with water, step still 5-6 min, after rinse legs with warm water.