BibTeX:
@incollection{AbdulBah1886,
  author = {'Abdu'l-Bahá},
  title = {A Dewdrop and the Ocean: The Báb's Promise Fulfilled},
  booktitle = {A Traveler's Narrative},
  year = {1886},
  publisher = {Cambridge University Press},
}

APA:
'Abdu'l-Bahá. (1886). A Dewdrop and the Ocean: The Báb's Promise Fulfilled. In *A Traveler's Narrative*. Cambridge University Press.

MLA:
'Abdu'l-Bahá. "A Dewdrop and the Ocean: The Báb's Promise Fulfilled." *A Traveler's Narrative*, Cambridge University Press, 1886.

Chicago:
'Abdu'l-Bahá. "A Dewdrop and the Ocean: The Báb's Promise Fulfilled." In *A Traveler's Narrative*, Cambridge University Press, 1886.