I had one of those weird moments of synchronicity today.
My novel has a fair number of mythological references (not too surprising as one of the central characters is a Greek goddess). I was editing a scene today in which one of the (non-goddess) characters is holding a glass of wine like a bowl in her two hands and another character thinks she looks like an oracle looking for answers in a scrying cup. Shortly afterwards the glass breaks and the goddess character has a ponder about bad luck quotas, 7 years for a mirror, how much for a glass?
I decided to Google the whole 'breaking a mirror = 7 years bad luck thing' and discovered that the 7 years bit goes back to the Romans who believed we renewed ourselves completely every 7 years and therefore that's how long a damaged soul (ie one that was broken when a mirror smashed) would take to heal. BUT the superstition goes back further than that, beyond early mirrors and polished shields and slices of obsidian, back to the scrying pools of dark water that were used for divination.
Wouldn't it be satisfying though if my novel ever gets published and I get a letter saying, "Did you know....?"