There's a brief description of the event in C.V. Wedgwood's book I found rather amusing. It's supposedly taken from Vilem Slavata's memoirs, though I'm curious how much is embellished.

"A hundred hands dragged them towards the high window, flung back the casement and hoisted them upwards. Martinitz went first. 'Jesu Maria! Help!' he screamed and crashed over the sill. Slavata fought longer, calling on the Blessed Virgin and clawing at the window frame under a rain of blows until someone knocked him senseless and the bleeding hands relaxed... One of the rebels leant over the ledge, jeering: 'We will see if your Mary can help you!' A second later, between exasperation and amazement, 'By God, his Mary has helped,' he exclaimed, for Martinitz was already stirring."