Although no longer studied much these days, cross correspondences were used predominantly between 1901 and 1932 as a way to test and validate the powers of mediums who were being studied by psychical researchers of the time. Although largely forgotten now, these compelling experiments may have actually offered worthwhile proof of paranormal powers. The correspondences were made up of information that was purportedly delivered to mediums by discarnate entities while the mediums were either in a trance state or through automatic writing.

There were three types of Cross Correspondences: simple, complex and ideal. In simple correspondences, two or more mediums produced the same word, words, phrases or similar phrases that were connected or related. In complex cross correspondences, messages are indirect and must be deciphered. Ideal correspondences involved messages that were incomplete and which had to be put together like a puzzle. Obviously, this opened these types of the messages to criticism however, there remains no real logical explanation for how these messages could occur. Some psychical researchers believed they provided strong evidence in support of survival after death but others believed that the mediums obtained the information from their own unconsciousness, from each other or from other living persons using telepathy or clairvoyance.

Myers died in 1901 but the first cross correspondences were produced by several mediums prior to his death. The messages were simple, showing similarities among the words spoken by mediums in trances and also by their automatic writings. The mediums were organized to be engaged in sittings at the same time, but in separate locations from one another. Eventually, the SPR would accumulate some 3,000 scripts.

Perhaps the most notable and convincing case for the validity of cross correspondences came from what was dubbed the "Palm Sunday Case". This unique case spanned more than 30 years and takes its name from the death of one of the communicators, Mary Catherine Lyttleton, known as May, who was born in 1850. As a vivacious and beautiful young woman, she attracted the interest of Arthur James Balfour, also from a  prestigious family, at their first meeting in 1870. They eventually fell in love and in 1875, Balfour told her of his intentions to propose marriage. Unfortunately though, after this meeting, he never saw her again. Lyttleton fell ill from typhus fever and died on March 21, 1875 -- Palm Sunday.

The first apparent communications in the Palm Sunday case occurred after the death of Frederic Myers. A short time after, Margaret Verrall, a friend of Myers and a classical lecturer at Newnham College, began receiving communications that seemed to come from Myers. They were veiled in symbolic references and laced with Latin and Greek terms and classical material.

In 1903, automatic writing began to come through to Alice Kipling Fleming, sister of Rudyard Kipling, and to Helen Verrall, Margaret Verrall's daughter, who was married to psychical researcher W.H. Salter. In 1908, Winifred Coombe-Tennant (later Willett) began to receive automatic writing scripts, also purportedly from Myers. She was related by marriage to Myers' wife. And while these ladies were the principal receivers of the material, a few messages were received by other individuals as well. All of the scripts were like those received by Margaret Verrall and were fragmentary and filled with obscure and classical references. All of them had mediumistic abilities of varying degrees but none of them knew the story of the Balfour-Lyttleton romance that had been cut short by death. Winifred Willett's scripts were later determined to have provided "introductory material" to what would emerge later during trances.

On January 16, 1907, thousands of miles away, the American medium Leonora Piper was in England conducting a séance for the SPR. While she was in a trance state, she was asked to give some sign when a cross correspondence was being attempted and one of the investigators suggested a triangle within a circle. A message attributed to Myers, suggested a "star" instead. Another "star" message came to Margaret Verrall a short time later and this theme was repeated in many of the communications that followed. On February 3, Helen Verrall also received a script that contained a number of drawings, including a star and a crescent moon, and were accompanied by an admonition that read: "The crescent moon, remember that and the star".

On February 11, the spirit communications were back with Leonora Piper and Myers wanted to make clear his knowledge of the messages given to the other mediums. Through Piper, he discussed an earlier message given to Margaret Verrall: "I referred to Hope and Browning," the script through Piper asserted. "I also said star ... look out for Hope, Star and Browning." On February 17, the Browning theme resurfaced in messages received by Helen Verrall. The spirit drew a star (through automatic writing) and then wrote: "That was the sign she will understand when she sees it .. no arts avail ... and a star above it all .. rats everywhere in Hamelin town..." The "Hamelin Town" Myers was apparently referring to the Browning poem about the Pied Piper of Hamelin. The reference made have also been a pun on the medium Leonora Piper's name. (During life, Myers loved puns and anagrams and the early cross correspondences are filled with them).

The scripts were analyzed by the SPR and it became apparent over a period of years that they were being produced by a group of discarnate beings were producing them. Some sense could be made by piecing them all together, yet the overall meaning and purpose of the messages remained a puzzle. A committee of investigators was formed to delve into the matter and included Gerald William Balfour (Arthur's younger brother); John George Piddington; Alice Johnson; Sir Oliver Lodge; and Eleanor Milfred Balfour Sidgwick. Their research seemed to reveal that the apparent purpose of the earlier communications was to announcing the continuing personalities of Mary Lyttleton and Francis Balfour, one of Arthur's brothers who had been killed in the Alps in 1882. In addition to Myers, Balfour and Lyttleton, other spirits allegedly included Henry Sidgwick and Edmund Gurney, both friends of Myers and founders of the SPR.

All of the messages that came through though seemed to be directed at Arthur Balfour, even though this was not immediately realized. Many of the symbolic references had personal meaning only to him and concerned Lyttleton and the circumstances surrounding her death. In the messages, Mary was referred to as the "palm maiden" and Arthur, the "faithful knight". Lyttleton was also identified by mentions of cockleshells or scallop shells, apparently in reference to the nursery rhyme, Mary, Mary Quite Contrary. The use of the symbols was apparently the preference for the spirits, who would not explain why. To make matters more frustrating, they were not in any hurry to reveal much of anything either -- until Arthur Balfour got involved in the case.

When given this information, Balfour at first refused to believe it, despite his desire to believe in survival after death. By this time, he was 64 years-old and 37 years had passed since Mary had died. He was stunned at the messages he was given and eventually agreed to sit with Willett while she tried to receive messages. Like the automatic writing scripts though, the information that came was cryptic and often indirect but started to make more sense as it was interpreted with the information that was known about Mary Lyttleton. The trance sessions became the focus of the case although Helen Verrall Salter and Margaret Verrall continued to receive messages via automatic writing until Margaret's death in 1916.