In his biography of Brown, Margaret Wise Brown: Awakened by the Moon, Leonard Marcus wrote that the two women visited museums together, in Paris. Among them was a trip to the Musée de Cluny... (p. 243-244):
... where the author of The Runaway Bunny surveyed the famed Unicorn tapestries, the fifteenth-century allegorical hunting scenes that filled an entire gallery with a picture book writ large. On their way out of the Cluny, Margaret purchased a set of postcards of the tapestries. "Wouldn't it be interesting," she said to her companion, "to make up a new story to go along with the pictures?" [45] She wanted to reorder the scenes, she explained, in such a way that the unicorn might elude his captors. At a nearby stationer that Margaret knew, she bought a parchment album. Returning to her hotel, they began rearranging the cards.
In time they had their story, and after inscribing it on the album's leaves Margaret said that it "would certainly be interesting to have the album bound in red leather."
The reason I'm honing in on those passages is that, according to Marcus, Virginia Mathews had a significant role in the creation of The Runaway Bunny. I wonder if I can find any books or articles that say more about Mathews and her role in the creation of that book?
Note: the passage above has "[45]" in it, which is a superscript in Marcus's book for a source note that reads "Virginia Mathews, 18 July 1984." It refers to an interview Marcus did of Mathews. Earlier in the notes section, there is a more complete reference to the interview: "Virginia Mathews, interview with author, Hamden, Conn., 18 July 1984."
I also wonder why, in the recent exhibits on children's literature at NYC and Minneapolis, Marcus makes no mention of the influence Mathews and her father had on Margaret Wise Brown.