An eyewitness reference to the Martyrdom of Tahirih by the Shah's Physician, Dr Jacob Eduard Polak, who was present at the execution.
This is a very rough translation by a friend - please email improvements if you have them.
Please see the end for references.
In late summer 1852 as the Shah, accompanied by an approximately 500-man guard, underwent an outing from his summer palace Riaveran, three men came towards him, whereupon one of them à bout portant fired a pistol at him, ... The shot grazed the stomach of the Shah's horse; the guard appeared to back off, leaving him to his fate, then everyone believed him to be dead and murdered at the hands of a pretender to the throne. Had there been a decaying corpse among the living it would have seemed superfluous [very loosely translated]. Only one foreign servant noticed the Shah stirring. He lunged dauntlessly and seized one of the murderers. A fight arose in which the servant received a stab wound to the stomach; in the meantime others trudged towards the murderers - and the king was saved. What resulted were only a few small grains of shot in the area of his backside. Of the assassins one recognised fanatical Babis, who wanted to avenge the death of their Prophet. The pistol and the ammunition which they operated were so poor that only a miracle could have enabled them realise their goal. The Shah immediately showed himself the wolf, in order to prevent malicious rumours... . He retorted that God had saved him: "Certainly God has saved me, because you all have forsaken me."
Then began the persecution. The Shah was encouraged to believe in a further widely networked conspiracy of Babis, shut up behind regiments, civil servants, attendants, priests, teachers, garden, in every sigh he found plotters[?] and he was not for a moment without fear for his life. Even the wife of the grand vizier, born in Masandaran, was accused belonging to the sect [...]. Seized by fear and horror from every side the Shah lapsed into Machiavellian ways to exterminate the believers. In Teheran there lived the highest of the royal farashe Haji Ali Chan, a heartless man and ready on command for any atrocity; he gave him the instruction to seek out all Babis and throw them in to jail. Then he ordered every corps, ever branch of the civilian and military detail to surrender at least one Babi in case within one or the other corps were still secret members of the sect [...].This plan should go ahead. Haji Ali an innovative mind came up with abominable, crucifying methods of execution [... passage about torture]. The martyrs demonstrated the courage and steadfastness of fanaticism; no recanting of faith, no hint of a cry of pain. I was witness to the execution of Qurret el ayn, who was executed by the war minister and his adjutants; the beautiful woman endured her slow death with superhuman strength [Ich war Zeuge von der Hinrichtung der Kurret el ayn, die vom Kriegsminister und seinen Adjutanten vollzogen wurde; die schöne Frau erduldete den langsamen Tod mit übermenschlicher Stärke.].
[ The New Zealand Star, Issue 9525, 24 April 1909, Page 2, has : "I was witness of the martyrdom of Karrattu'l Ayn, who was murdered by the Minister of War and his adjutants. The beautiful woman endured a lingering death with superhuman fortitude."]
PDF Original (157 K, Section Translated) : http://www.paintdrawer.co.uk/david/folders/Research/Bahai/Tahirih/Persien%20das%20Land%20und%20seine%20Bewohner%20-%20Jakob%20Eduard%20Polak%20p380-382.pdf
PDF Original (26 Mb, Whole Book) : http://books.google.com/books?id=IvAIAAAAIAAJ&oe=UTF-8
Full Page Reference : Persien Das land und Seine Bewohner by Jakob Eduard Polak, from Page 351 (Google PDF page 380), bottom paragraph, ''Als im Spaetsommer 1852...'', up to page 353 (PDF page 382), "langsamen Tod mit übermenschlicher Stärke...''