What was the first works about the holy grail?

The first known works about the Holy Grail can be traced back to the medieval romances of the 12th century, particularly in the writings of Chrétien de Troyes. His poem "Perceval, the Story of the Grail," composed around 1180, introduced the Grail as a mystical object associated with divine grace. This concept was further developed in later works, such as the "Queste del Saint Graal," part of the larger Arthurian legend, which elaborated on the Grail's significance in the quest for spiritual enlightenment.