Lovecraft On Houdini via letter to Frank B. Long

In a letter to Frank Belknap Long dated February 14, 1924, HPL wrote:
It seems that once Houdini was in Cairo with his wife on a non-professional pleasure trip, when his Arab guide became involved in a street fight with another Arab. In accordance with custom, the natives decided to fight it out that night on the top of the Great Pyramid; and Houdini's guide, knowing the magician's interest in exotic oddities, invited him to go along with his party of seconds and supporters. Houdini did, and saw a tame fistic encounter followed by an equally mechanical reconciliation. There was something off-colour and rehearsed about it all, and the wizard was hardly surprised when suddenly the frame-up was revealed, and he found himself bound and gagged by the two Arabs who had faked the combat. It had all been prearranged--the natives had heard of him as a mighty wizard of the West, and were determined to test his powers in a land where wizards had once ruled supreme. Without ceremony they took him to an aperture in the roof of the Temple of the Pharaoh's (Campbell's Tomb) where a sheer drop of fifty-three feet brings one to the floor of the nighted crypt which has but one normal entrance--a winding passage very far from this well-like opening. Producing a long rope, they lowered him into this abode of darkness and death and left him there without means of ascent--bound and gagged amidst the kingly dead, and ignorant of how to find the real exit. Hours later he staggered out of that real exit, free, yet shaken to the core with some hideous experience about which he hesitates to talk. It will be my job to invent the incident, and give it my most macabre touches. As yet, I don't know how far I can go, since from a specimen Houdini story which Henneberger sent me I judge that the magician tries to pass off these Munchausens as real adventures. He's extremely egotistical, as one can see at a glance. But in any case, I guess I can weave in some pretty shocking things ... unsuspected lower caverns, a burning light amidst the balsam'd dead, or a terrible fate for the Arab guides who sought to frighten Our Hero.