The psychomantium is a gazing mirror used for making contact with those who have passed on. Dr. Raymond Moody (of the book "Life After Life" fame) made this ancient technique popular with his book "Reunions: Visionary Encounters With Departed Loved Ones."
The best description I’ve found of this technique comes from this website’s description:
The initial setup is a little more complex and costly than that of a scrying mirror. A large mirror (4' high by 3-1\2' wide) is attached to a wall with the bottom edge about 3' from the floor. A comfortable, high backed chair is placed about 3' from the mirror. The top of the backrest of the chair should be below the bottom of the mirror. The feet of the chair should be trimmed to allow the chair to slant farther back than is normal.
The person sitting in the chair should not be able to see his/her reflection in the mirror. The area around the chair and mirror is surrounded by a black velvet curtain. This black void should be all that is reflected in the mirror. A lamp with a 15 watt bulb is placed behind the chair. This is the only illumination in the room.
This procedure is usually performed after dark to alleviate the problem of light entering the room through the windows. Thick, dark curtains or a room without windows would allow you to use the psychomantium even during the day.
Proper mental preparation is essential for this procedure to work. Dr. Moody starts his participants at 10:00 AM. They are requested to bring personal items from the deceased person that is to be contacted. Throughout the day they discuss the deceased. At dusk the participant enters the psychomantium. He/she is told to stay as long as they like. They were also told to blank their mind except for thoughts of the deceased and to gaze into the mirror.
Although my own experience with using a psychomantium is minimal (two sessions), I can attest to the fact that at one point a dark man’s shape appeared in the mirror and he stood there for some time before stepping back and out of sight. Whether that was an actual spirit or not is, of course, impossible to prove or that he might have been my eyes trying to see something in the dark and interpreting in the setting of expecting to see a spirit.
I would never advise people using this during periods of grief or those seeking a kind of resolution with souls of the departed. This is purely for experimental purposes and best used by people who have no existing emotional issues that might cloud the experience or leave them frightened. I would also want to exclude those of a highly religious background, as they might be more likely to fight against the taboo notions and hysteria that goes with trying to communicate with the dead. A lot of people, even as grownups, do not like gazing into mirrors in dim lighting. Highly suggestible people are most susceptible to ill effects and bad reactions.
Generally, if a Ouija board scares you, this will scare you just as much.
If you decide to experience a psychomantium encounter, do not do so alone. Whether you realize it or not, just the active trying to create a portal to the dead can make feelings erupt and having someone there to sort it through with is helpful.
I think the advantage of using this method is that it forces focus, like ghost hunting when we do it in the dark and quiet - we hear every sound, notice every shadow. When there is nothing to distract you and you are calling upon the dead, you have a combination that makes you a great receiver. This is about preparing your ability to perceive, not about creating a place ghosts like to hang out. They are there, but many of us do not get in the frame of mind to notice them.
I personally would like to put one in my writer’s office. Some folks keep stationary bikes in an office, but this would be a fantastic way to open me up and help me with my horror writing, a sort of focusing tool, like walking a labyrinth or meditation.
Whether you believe in the phenomenon of psychomantiums or not, they have been with man for a very long time (ancient Greeks) and will continue to be a curiosity for the living.