Thomas Bradford of Detroit, Michigan was a spiritualist who was such a believer in the afterlife that he killed himself to prove it. So in 1921, he placed an ad in the newspaper seeking an assistant for an experiment in "spiritualistic science." A respected writer from a prominent area family, Ruth Doran listened to Bradford explain that "there was but one way to solve the mystery [of the afterlife]—two minds properly attuned, one of which must shed its earthly mantle." She agreed and promised that after his death, she'd hold seances and keep her ears (and mind) open for messages from the great beyond. Apparently with great confidence, Bradford extinguished his heater's pilot light and sat in his room until the gas did him in. From Mysterious Universe:
An investigation was launched, and although Doran was at first seen as highly suspicious or at the very least complicit in the death, it would be ruled a suicide and she would claim that she had not seriously believed Bradford would actually go through with it […]
Doran did her part, dutifully keeping constant vigil and holding regular séances, but there was no response from Bradford.
As Doran kept trying, a psychic medium by the name of Lulu Mack came forward to claim that she had been contacted by Bradford when he called out to her during a séance and said his name. Mack, who claimed that she had never heard of Bradford before that, explained that he had indeed been strenulously trying to communicate from the other side, but that his spirit was too weak because he had died of a suicide. She said that he was only in "the first sphere of the heavenly constellation," so she was getting only garbled messages from Bradford, but she would not be able to fully understand what he was trying to say until he strengthened his spirit by reaching a different "heavenly altitude," a process that she said could take years.
Eventually, Doran herself felt that Bradford had contacted her and she enlisted a whole group of spiritualists to help receive his message. Bradford reportedly delivered the following message which unfortunately would be his last:
I am the professor who speaks to you from the Beyond. I have broken through the veil. The help of the living has greatly assisted me. I simply went to sleep. I woke up and at first did not realize that I had passed on. I find no great change apparent. I expected things to be much different. They are not. Human forms are retained in outline but not in the physical. I have not traveled far. I am still much in the darkness. I see many people. They appear natural. There is a lightness of responsibility here unlike in life. One feels full of rapture and happiness. Persons of like natures associate. I am associated with other investigators. I do not repent my act. My present plane is but the first series. I am still investigating the future planes regarding which we in this plane are as ignorant as are earthly beings of the life just beyond human life.
"The Time a Spiritualist Killed Himself to Prove a Life After Death" (Mysterious Universe)