BibTeX:
@incollection{Various,
  author = {Various},
  title = {The Royal Penmanship},
  booktitle = {bahaistories.com archive},
  url = {https://bahaistories.com/subject/bahaullah-sulaymaniyyih},
}

APA:
Various. The Royal Penmanship. In *bahaistories.com archive*.

MLA:
Various. "The Royal Penmanship." *bahaistories.com archive*, n.d..

Chicago:
Various. "The Royal Penmanship." In *bahaistories.com archive*, n.d..