This one is really interesting and as far as I know it can be described as Retrocognition ("backward, behind" knowledge of a past event which could not have been learned or inferred by normal means)
On August 10, 1901 two English women visited the gardens of the Petit Trianon near Versailles. The controversy over exactly what these women saw there on that day would linger on for decades.
The two women were Anne Moberly and Eleanor Jourdain, both academics, principal and vice-principal respectively of St. Hugh's College, Oxford. They were on vacation in France and decided to spend a day at Versailles. They first toured the palace and then agreed to explore the grounds in search of the Petit Trianon. Here is a rough account of what happened next:
They began searching for the Petit Trianon but became lost. As they wandered, they passed a deserted farmhouse and noticed an old plough lying by the side of the road. Immediately, they both began to feel strange, as if a heavy mood was oppressing their spirits. Two men dressed in "long greyish-green coats with small three-cornered hats" passed them. The women asked these men the way to the Petit Trianon and were directed down a path directly in front of them. They proceeded down this path until they came upon a gazebo shaded by trees. The dark mood hung even heavier over them here. Everything was very still. A repulsive looking man, his face pitted with small-pox was standing by the gazebo, and he stared unpleasantly at them.
Just then someone came rushing up behind them and warned them that they were going the wrong way. They were told to cross a small bridge, and when they did so they arrived at what they assumed to be the Petit Trianon. Here a woman was sitting on a stool, sketching. She wore an old-fashioned dress, covered with a pale green scarf. Again, they experienced a sensation of intense gloom. Suddenly a footman came rushing out of a nearby building, slamming the door behind himself. The footman told them that the entrance to the Petit Trianon was on the other side of the building, and so they walked around the house where they found a wedding party waiting to tour the rooms. The dark mood lifted, and nothing else unusual happened.
Three months later, back in England, Moberly happened to mention the sketching woman to Jourdain. Jourdain declared that she had not seen such a woman. They were intrigued by this element of mystery. How could one of them have seen a figure and not the other? When they further compared recollections they both remembered feeling that something strange had occurred in the garden, so they decided to each write down a separate account of what they had seen and compare notes.
It turned out that there were a number of figures whom Moberly had seen whom Jourdain had not, but on other details they agreed. Investigating further, Jourdain discovered that the day on which they had visited the palace was the anniversary of the sacking of the Tuileries in 1792, when Louis XVI and Marie Antoinette had witnessed the massacre of their Swiss Guards and had been imprisoned in the Hall of the Assembly.
The two began to wonder if they had somehow seen the ghost of Marie Antoinette, or rather, if they had somehow telepathically entered into one of the Queen's memories left behind in that location. As if to confirm their suspicion, Moberly came across a picture of Marie Antoinette drawn by the artist Wertmüller. To her astonishment it depicted the same sketching woman she had seen near the Petit Trianon. Even the clothes were the same.
Intrigued by the growing mystery, Jourdain returned to Versailles in January 1902 and discovered that she was unable to retrace their earlier steps. The grounds seemed mysteriously altered. She then learned that on October 5, 1789 Marie Antoinette had been sitting at the Petit Trianon when she first learned that a mob from Paris was marching towards the palace gates. Jourdain and Moberly decided that Marie Antoinette's memory of this terrifying moment must have somehow lingered and persisted through the years, and it was into this memory that they had inadvertently stumbled. This explained the sensation of dark depression they had felt at the time.
The two women sent a letter to the Society for Psychical Research declaring their discovery that the Trianon was haunted. But the Society deemed their claims unworthy of investigation. Thereupon the two women decided to conduct a full-scale investigation of their own to prove that they had seen the ghost of Marie Antoinette. The accounts of Versailles they wrote in 1901 were the corner-stone of this investigation. They sought to prove that in these accounts they had accurately described what Versailles looked like in 1789. Their argument was that because they did not possess any knowledge of eighteenth-century Versailles when they wrote these accounts, it would have been impossible for them to produce such detailed descriptions unless the scene they had witnessed really was Marie Antoinette's memory of 1789 Versailles that they had somehow stumbled into.
The result of their investigation was the publication in 1911 of a book titled An Adventure. They published it under the pseudonyms of Miss Morison and Miss Lamont. This is some of the evidence they unearthed:
They had seen a plough, but on later trips they learned that no ploughs had been kept in the gardens of Versailles in 1901. However, an old plough had been displayed on the grounds in 1789.
They had crossed a small bridge, but on later trips they could not locate this same bridge. However, they discovered that a bridge had existed there in 1789.
They had seen two men in green coats. These men, they later learned, were wearing the uniform of Marie Antoinette's Swiss Guard.
They had seen a sinister, pock-marked man. This man exactly resembled Comte de Vaudreuil, an enemy of Marie Antoinette.
They saw a footman rush out of a building and slam a door shut behind himself. However, this door was actually barred and bolted shut when they visited, and had been kept so for many years.
Finally, the sketching lady herself could have been no one else but Marie Antoinette.
An Adventure provoked an outpouring of public interest, selling 11,000 copies by 1913. But it also attracted a great deal of criticism. Critics argued that the two women either simply got lost, or their memories of what they had seen were mistaken.
The two women defended themselves, and published the accounts of their experience that they had each written in November 1901 as proof that they had seen things which they later discovered corresponded exactly to what the grounds of Versailles looked like in 1789. They argued that there was no way they could have known about such details.
After the women died (Jourdain in 1924, Moberly in 1937) their identities were revealed. The revelation that they were respected academics created further interest in the case, and a series of studies of the case followed.
The most damaging analysis of their claims appeared in 1950, written by W.H. Salter. Salter concluded, based upon a close review of Jourdain and Moberly's correspondence with the Society for Psychical Research, that many details included in the accounts they had (supposedly) written in 1901 had actually been added at a much later date, in 1906, after the women had conducted extensive historical research. This discovery cast serious doubt upon their claims, because their entire case had rested upon the impossibility of the two of them, in 1901, being able to give an accurate description of 1789 Versailles.
It is likely that the two women sincerely believed that they saw something mysterious on their visit to Versailles in 1901. But they so badly wanted others to believe that they had seen something that, whether consciously or not, they embellished their evidence. In this way they managed to reassure themselves of the reality of their ghost sighting and simultaneously persuaded a significant portion of the public to share their belief.