In the the Summer 1945 issue of a fanzine called The Acolyte was published a short memoir called “Interlude with Lovecraft” by Stuart Morton Boland, which began:
In the Spring of 1935 I was making a library survey tour of the European continent. At the quaint little hill town of Orvieto, in Italy, I came upon an amazing mural high on the walls of the local Duomo or Cathedral. The painting represented mighty figures of ebon-hued men (not angels or demons) with great wings, flying through etheric space carrying beauteous pinionless mortals--men and women who were rapturously accompanying them in their voyage through eternity.
I photographed the scene and sent a print to Robert E. Howard, telling him it reminded me of one of his Conan stories. With the print I included a colored reproduction of a rare illuminated manuscript of the 10th Century which I had seen in the Royal Archives at Budapest. Howard, for some reason, sent this facsimile to Lovecraft, asking if he thought his Necronomicon would look anything like the reproduction of the parchment.
Three months later, when I reached my home by the Presidio in San Francisco, I found awaiting me two letters from Howard and an extensive missive from Lovecraft. [...] In my reply to HPL, I stated that I thought his opinion was well-founded, and furthermore that the references of both men to odd ancient gods were ideas they must have borrowed from Mayan, Toltec, and Aztec mythology. (Boland 15)
This presents an interesting example of the consideration of historical evidence, because aside from statements from Boland, there is no direct evidence that Boland and Robert E. Howard ever corresponded. Boland wrote to Glenn Lord in the late 1950s: