When an object is held or touched by a person, especially if the object is owned exclusively by the person, it becomes 'imprinted' by them. Physical, emotional and psychological aspects of the owner may be picked up by a psychic.
The psychic will hold the object and go into a state of calmness or meditation and 'pick up' many aspects of the owner's past, present and future.
When someone picks a flower from a garden or field and hands it to the psychic without anyone else touching it, the psychic will be able to 'pick up' the imprint of the person who picked it.
Sand or water readings work in a similar way. When a person touches a bowl of sand or water, a psychic should be able to hold their hands above the bowl and gain similar information about the person who left the 'imprint'.
Psychometry is a useful addition to a tarot card reading to 'extend' the reading and provide additional information.