Etta Wriedt

[1] Wriedt was born in Oswego, New York[2] and was well known in the field of spiritualism, she employed a trumpet in the darkness of the séance room which she claimed spirits would use to make noises and voices.

She charged people money to attend her séances, one of her spirit guides was "John Sharp" who claimed he was born in Glasgow, Scotland, in the eighteenth century.

[7][8] Wriedt was exposed as a fraud by the physicist Kristian Birkeland when he discovered the noises produced by her trumpet were caused by chemical explosions induced by potassium and water and in other cases by lycopodium powder.

[9] Joseph McCabe wrote: [Birkeland] jumped up, switched on the electric light, and, before the Spiritualists could interfere, had snatched the two trumpets from the floor...

Mrs. Wriedt had put in the trumpet particles of metallic potassium which, meeting the moisture she had also thoughtfully provided, explained the "psychic movements."