The Heraclean Stone

"This ability of yours is a divine power which moves you, like the power in the stone which Euripides calls a magnet, but which most people call the Heraclean stone. This stone not only attracts iron rings, it also confers on them the power to do the same, that is, to attract other rings, so that sometimes a long chain of rings and pieces of iron, suspended one from another, is formed, the power of them all depending on the stone.

In the same way the Muse herself inspires people, and from these inspired people a chain of others is strung out, all inspired with the same enthusiasm."
-Socrates on poetry, in Plato's "Ion"