Pascal "Pat" Covici and Steinbeck's friendship began when Pat published Tortilla Flat (1935). As Steinbeck wrote Journal of a Novel: The East of Eden Letters, he often mentioned the things he was tinkering with or building around the house. At one point, Pat asked Steinbeck to make him a box; Steinbeck joked that the only specification was that Pat shouldn't be able to fit inside it.

When Steinbeck finished East of Eden, he placed his 250,000 word manuscript into a mahogany box he had carved and sent it to Pat. The note he placed on top became the dedication page of the novel.

Dear Pat,
You came upon me carving some kind of little figure out of wood and you said, "Why don't you make something for me?"
I asked you what you wanted, and you said, "A box."
"What for?"
"To put things in."
"What things?"
"Whatever you have," you said.
Well, here's your box. Nearly everything I have is in it, and it is not full. Pain and excitement are in it, and feeling good or bad and evil thoughts and good thoughts—the pleasure of design and some despair and the indescribable joy of creation.
And on top of these are all the gratitude and love I have for you.
And still, the box is not full.