The Feast of the Lemures, called the Lemuralia or Lemuria was a feast during which the ancient Romans performed rites to exorcise the malevolent and fearful ghosts of the dead from their homes. On those days, the Vestals would prepare sacred mola salsa (salt cake) from the first ears of wheat of the season.
In the Julian calendar the three days of the feast were the 9th, 11th, and 13th of May. The myth of origin of this ancient festival was that it had been instituted by Romulus to appease the spirit of Remus (Ovid, Fasti, verse 473ff.). Ovid notes that at this festival it was the custom to appease or expel the evil spirits by walking barefoot and throwing black beans over the shoulder at night. It was the head of the household who was responsible for getting up at midnight and walking around the house with bare feet throwing out black beans and repeating the incantation, "With these beans I redeem me and mine" nine times. The household would then clash bronze pots while repeating, "Ghosts of my fathers and ancestors, be gone!" nine times.
Because of this annual exorcism of the restless malevolent spirits of the dead, the whole month of May was rendered unlucky for marriages, whence the proverb Mense Maio malae nubent ('They wed ill who wed in May'), and thus the rush of June weddings "because the weather is so nice" in our own day.