The two very heavy chains that Baha’u’llah “was weighted and tormented by”

If sometime thou shouldst happen to visit the prison of His Majesty the Sháh, ask thou the director and chief of that place to show thee those two chains, one of which is known as Qará-Guhar and the other as Salásil. I swear by the Day-star of Justice, that during four months, I was weighted and tormented by one of these chains. ‘The sorrow of Jacob paleth before my sorrow; and all the afflictions of Job were but a part of my calamities.’ 

- Baha’u’llah  (‘The Epistle to the Son of the Wolf’)

“chains of such weight as only notorious criminals were condemned to carry, were placed upon His [Bahá’u’lláh’s] neck”

One of the chains placed around Bahá’u’lláh’s neck in the Síyáh-Chál