OVID'S METAMORPHOSES, PG. 109

Demeter, or Ceres, first plowed the land and gave the men the gift of bringing forth crop from the tilled earth. Proserpine, Demeter's beloved daughter, was captured by Hades, who took her to the underworld and made her his queen. Demeter mourned the loss of her daughter, and then, the soil bared no fruits or crops for man to eat. Thus winter came upon the land. Eventually Hades was forced to let Proserpine go. However, while in the underworld Proserpine ate four seeds, which resulted in her having to return to the underworld for four months out of the year, and at that time Demeter mourns and we have winter.