Spilling salt

A superstition in Western cultures holds that spilling salt is an evil omen. However, salt has had a variety of meanings in religions around the world.
History.
The European belief in the ill luck that comes from spilt salt is quite old, going back to ancient Rome. The 1556 "Hieroglyphica" of Piero Valeriano Bolzani reports that "(s)alt was formerly a symbol of friendship, because of its lasting quality. For it makes substances more compact and preserves them for a long time: hence it was usually presented to guests before other food, to signify the abiding strength of friendship. Wherefore many consider it ominous to spill salt on the table, and, on the other hand, propitious to spill wine, especially if unmixed with water."
This may not be the actual explanation since salt was a valuable commodity in ancient times and, as such, was seen as a symbol of trust and friendship. A German proverb held that "whoever spills salt arouses enmity". According to Charles Nodier, among "savages", the "action of spilling salt ... indicates among them the refusal of protection and hospitality from such strangers as they may have reason to suspect are thieves and murderers."
This led to the common misconception that due to salt being such a valuable item Roman soldiers were paid in it. There is no historical evidence for this belief. The idea is so widely held and has been for so long that the etymology of the word salary comes from the Latin "salarium" was originally salt money (Lat. "sal", salt), "i.e." the sum paid to soldiers for salt.
One widespread explanation of the belief that it is unlucky to spill salt is that Judas Iscariot spilled the salt at the Last Supper and indeed Leonardo da Vinci's "The Last Supper" depicts Judas Iscariot having knocked over a salt-cellar. This is often taken as a questionable explanation because spilling salt was generally considered a bad omen already and indeed the imagery predates Leonardo's usage.
Some have scoffed at the omen. Herbert Spencer wrote that "A consciousness in which there lives the idea that spilling salt will be followed by some evil, obviously allied as it is to the consciousness of the savage, filled with beliefs in omens and charms, gives a home to other beliefs like those of the savage." Even now a variety of methods are used to avert the evil omen of spilled salt. The most common contemporary belief requires you to toss a pinch of the spilt salt over your left shoulder, into the face of the Devil who lurks there. Though generally disregarded as an ineffectual superstition, Professor Jane Risen of Chicago University has published research that shows such "jinx avoidance behavior" can have a positive effect on people's actions after a perceived bad luck event.
Salt in religions throughout the world.
One of the reasons that this superstition has been so enduring and widespread is that salt has long held an important place in religions of many cultures.