Which medieval poet made the Grail a stone called lapsit exillis in his poem Parzival?

Wolfram von Eschenbach made the Grail a stone called lapsit exillis in his early 13th-century poem Parzival.

Wolfram’s Parzival is one of the most important German adaptations of the Perceval story. Unlike later popular imagery that usually shows a chalice, Wolfram describes the Grail as a precious, wondrous stone guarded by the Grail community. The stone provides extraordinary nourishment, helped by a magical inscription and a dove associated with its renewal.

Wolfram drew on Chrétien de Troyes but also claimed to have used a source connected with a figure named Kyot. Scholars debate whether Kyot was historical or a literary invention. His version also gives the Grail knight a distinctive family history and places the action in a wider world than many French romances.

The phrase lapsit exillis is famously enigmatic. It is often interpreted as a corrupted or stylized Latin expression, but its exact meaning remains uncertain.