The Síyáh-Chál, the Black Pit, was a disused underground water reservoir beneath a public bath in Tehran, used as a dungeon. Bahá'u'lláh was confined there for four months in 1852 after an attempt on the life of Násiri'd-Dín Sháh by two Bábís acting without authorisation, an act that triggered a massacre of the community. The pit held around a hundred and fifty prisoners in total darkness with no ventilation; a chain called the Qará-Guhar, weighing over a hundred pounds, was fastened round his neck, and the scars it left were permanent. He describes in the Epistle to the Son of the Wolf and elsewhere the experience of that confinement — a sensation as of something flowing from the crown of his head over his breast, and the appearance of a Maiden suspended in the air before him — as the beginning of the revelation. The Bahá'í dating of Bahá'u'lláh's prophetic consciousness to those four months is central: the faith locates its origin in a hole in the ground under a bathhouse.