In his prose work The Sea of Cortez, a work which describes Steinbeck's and Ed Rickett's explorations in the Gulf of California, Steinbeck reports a story that he heard in the lower California Peninsula; it was reported as a true story occurring in "La Paz in recent years." Steinbeck writes:
An Indian boy, by accident, found a pearl of great size, an unbelievable pearl. He knew its value was so great that he need never work again. In this one pearl he had the ability to be drunk as long as he wished, to marry any one of a number of girls, and to make many more a little happy too. In his great pearl lay salvation, for he could in advance purchase masses sufficient to pop him out of purgatory like a squeezed watermelon seed. In addition, he could shift a number of dead relatives a little nearer to Paradise.
The original story continues by pointing out how every pearl buyer to whom he tried to sell the pearl offered such a small price that the young Indian finally refused to sell the pearl and, instead, hid it under a rock. For two nights in a row, the young man was attacked and beaten. Then, on the third night, he was ambushed and tortured, but still he refused to reveal the whereabouts of the Pearl of the World. Finally, after careful planning, he "skulked like a hunted fox to the beach," removed the pearl from its hiding place and threw it back into the Gulf.
As with other great writers, notably Shakespeare, who took all of his plots or stories from other sources, it is not the source itself that is so important as it is what Steinbeck does with his sources. The above legend is the bare outline, but we should notice all of the significant changes that Steinbeck makes. First, the simplicity of the above parable is made much more complicated in Steinbeck's novel. Instead of having an irresponsible boy who will use the pearl principally for the seduction of young girls and for whimsical prayers for relatives in Purgatory, Steinbeck changes the boy into a father and a husband, a man who sees in the pearl the opportunity to buy an education for his son and thus free him from the bonds that he and his family have always lived under. Furthermore, the other dreams — being married in the church, baptism for their son, new tools to help Kino in his trade, etc., — contrast sharply to the youth in the anecdote.
Whereas the young Indian boy is a simple, flat character, Steinbeck takes the character, gives him a name (Kino) that is based upon a seventeenth-century missionary (who was considered a great man, as the priest points out), and Steinbeck endows him with all of the primitive but human characteristics befitting the hero of a parable such as The Pearl. In addition, Steinbeck expands upon his story by the addition of all types of supporting characters — the brother, the priest, the trackers, and, most important, Juana. Steinbeck does, however, retain the pearl buyers, who become forces which are aligned to others with the intent to destroy Kino.
Thus, while Steinbeck begins his story with a simple folk story, he takes the basic situation and, using all sorts of illusions from Western literature, he enriches the basic story and adds various symbolic levels of meaning to it.