It concerns a flat (apartment) with a very peculiar effect on people. I might add that, although the author - who was a very prominent psychic researcher of his day - described the phenomenon as a "poltergeist", there is not the slightest evidence to that effect, and no other poltergeist manifestations were present. Any reasonable explanation will be welcome.
A very amusing Poltergeist case was reported in the Daily Mail [England] for May 1, 1907. An elderly woman, Mme Blerotti, called on the magistrate of the Sainte Marguérite district of Paris and complained that 'something' in her flat compelled her to enter her home on her hands, with her legs in the air. She simply could not resist employing this peculiar mode of locomotion. The magistrate detained her (thinking she was mad) and sent a sergent de ville to the address given. He returned with the woman's son, a bank clerk, aged twenty-seven, who said: 'What my mother has told you is true. I do not pretend to explain it. I only know that when my mother, my uncle, and myself enter the flat, we are immediately impelled to walk on our hands.' Then the uncle, Paul Reiss, who lived with them, was sent for and he told them the same story. He, too, when he entered the flat, could not walk the right way up. Finally, the concierge of the building was brought before the magistrate. 'All that you have heard is true' said he. 'I thought that my tenants had gone mad, but as soon as I entered the rooms occupied by them, I found myself on all fours, endeavouring to throw my feet in the air.' The magistrate ordered the rooms to be disinfected!!
Reference: Harry Price (1946), Poltergeist Over England, Country Life, London, chapter 3. Republished in 1994 by Studio Editions as Poltergeist, p 28.