In 1922 - a little over three decades after psychical researchers Edmund Gurney, Frederic Myers, and Frank Podmore had initially published their classic two-volume anthology Phantasms of the Living  - there appeared a second notable anthology of reported psychic experiences which had been diligently compiled and examined by another psychical researcher, Eleanor Sidgwick.  Meant be a sequel of sorts to the work of Gurney and his colleagues, Mrs. Sidgwick's anthology contained 200 additional written accounts gathered from the case collection of the Society for Psychical Research, covering the period from 1886 to 1920 (essentially picking up where Gurney and his colleagues had left off). Among those 200 cases was the following one, which seems rather fitting to relate here on the occasion of Mother's Day:
A little friend of ours, H. G., had been ill a long time. His mother, who was my greatest friend, had nursed her boy with infinite care, and during her short last illness, was full of [anxiety and concern] for him.
After her death, he seemed to become stronger for a time, but again grew very ill, and needed the most constant care, his eldest sister watching over him as the mother had done. As I was on the most intimate terms with the family, I saw a great deal of the [ailing boy].
On Sunday evening, June 28th, 1903, about 9 o'clock, I and the sister were standing at the foot of the bed, watching the sick one, who was unconscious, when suddenly I saw the mother distinctly. She was in her ordinary dress as when with us; nothing supernatural in her appearance. She was bending over her boy with a look of infinite love and longing and did not seem to notice us. After a minute or two she quietly and suddenly was not there. I was so struck that I turned to speak to the sister, but she seemed so engrossed that I did not think it wise to say anything.
The little patient grew gradually worse, until on Tuesday evening, June 30th, I was summoned to go at once. When I arrived at the house, he had passed away. After rendering the last offices of love to the dear little body, the sister and I again stood, as on the Sunday, when I said, "M--- [the sister's name], I had a strange experience on Sunday evening here." She quickly replied, "Yes, Mother was here; I saw her." The young girl is not given to fancies at all, and must have been impressed as I was. [2, pp. 378 - 379]
Assuming that it took place as recounted, this case would appear to represent a collectively-witnessed apparitional experience that was not influenced by suggestive verbal cues being passed between the witnesses (as it seems that the writer did not tell the elder sister about what she'd seen before the sister revealed that she'd seen the mother's spectral figure, as well).
It also appears to represent what the late parapsychologist Louisa Rhine had termed a "bystander-type" case, in which one of the witnesses sees the apparition of a certain individual (the deceased mother) in close proximity to one or more people (the ailing boy and his elder sister) who'd once known that individual in life. As Rhine herself observed, these kinds of cases "...are suggestive of the haunting cases, the main difference, however, being that in these the [psychic] link is a person [or persons, in this particular instance] rather than a geographical location." [3, p. 39]
Another case cited by Rhine which seems to have a similar bystander-type aspect to it (and which also involves the sighting of a mother's spectral figure) is the following one, which comes from her own extensive case collection:
My aunt, who raised me, died January 25th of a cerebral hemorrhage. She had a stroke the Friday before. We had all been up for five days and nights with her. I had been to my room for a cup of tea and my husband was with "Mom," as we called her. He was saying the rosary at her bedside. The candles were flickering and she was in a coma. All of a sudden he ran down the stairs with his face white and was visibly shaken. When we could get him to talk, he said that while he was praying, Mom seemed to come to and started flaying her arms about, holding them up in the air as if trying to reach someone and saying, "Mom, oh Mom." My husband felt a breeze and then alongside of him stood a little woman less than five feet tall with a plaid shawl over her head, wringing her hands, and my husband saw tears running down her face. Although he heard nothing from the woman, he heard the rustling of her dress. She was in black. He said that he prayed hard that he could get the strength to leave the room. When able, he rushed out and down the stairs. He told his experience to relatives there and an aunt by marriage said, "Well, that was her mother. She had been dead since 1910." When we went upstairs, Mom was dead with a peaceful smile on her face. [3, p.38]
Here the bystanding witness (the husband) also sees the apparition of a certain individual (the deceased mother) in close proximity to someone (the dying aunt) who'd known that individual in life. Interestingly, this particular case could also be classified as a deathbed vision (where an apparition of the dead is seen by a terminally-ill patient very close to the time of death - see Ref. 4 for examples), since it appears that dying aunt had also witnessed the figure, as well.
The PRF offers pleasant wishes to all mothers on their special day!
 Gurney, E., Myers, F. W. H., & Podmore, F. (1886). Phantasms of the Living (2 vols.). London: Trubner & Company, Ltd.
 Sidgwick, E. M. [Mrs. H.] (1922). Phantasms of the living: An examination and analysis of cases of telepathy between living persons printed in the "Journal" of the Society for Psychical Research since the publication of the book "Phantasms of the Living" by Gurney, Myers, and Podmore in 1886. Proceedings of the Society for Psychical Research, 33, 23 - 429.
 Rhine, L. E. (1957). Hallucinatory psi experiences: II. The initiative of the percipient in hallucinations of the living, the dying, and the dead. Journal of Parapsychology, 21, 13 - 46.
 Osis, K., & Haraldsson, E. (1977). At the Hour of Death. New York: Avon Books.