[quote=@KabenSaal]
In 'Gugure! Kokkuri-san' the self-proclaimed doll throws salt at Kokkuri-san, a spirit.
[/quote]

I looked it up. Gugure! Kokkuri-san was serialized in 2011. Supernatural has been on the air since 2005. By the time Gugure! Kokkuri-san was written Supernatural was well into its sixth season. By that point it was popular enough that its popularization of using salt against demons and ghosts would be known even by those that weren't a fan of the show. More than likely the writer got the idea even if indirectly from Supernatural and not some old mythology or legend.