My Nana used to tell me a tale about when she had wet tears on her cheek, but not from her eyes, she said it usually happened prior to a death of someone close like in the family or relatives. She experienced it when her son (my uncle) died in southern Italy during WW2. My uncle couldn't swim, drowned after the Gerries sunk their navy ship they were on. My Nana also said there was a knock at her window. When she looked, it was the black death watch Beatle tapping on the glass. It could be a warning of a death, or an already deceased trying to contact you. I'm only going my my Nana's claims here.. otherwise dunno what it is myself.