Conversation so far:
Who first tested Garret's abilities?
One of the tests was organized by Joseph Rhine at Duke University in 1933 which involved Zener cards.
Describe the test?
Certain symbols that were placed on the cards and sealed in an envelope, and participants were asked to guess their contents.
What were the results of the test?
She performed poorly and later criticized the tests by claiming the cards lacked a psychic energy called "energy stimulus" and that she could not perform clairvoyance to order.
What other tests were done?
The parapsychologist Samuel Soal and his colleagues tested Garrett in May 1937.

Question: How was this test performed?
Self-contained rewrite: How was the test by Samuel Soal and his colleagues in May 1937 performed?