Ichabod references Thomas Jefferson taking a scalpel to his Bible. Jefferson actually did this with several Bibles, constructing the The Life and Morals of Jesus of Nazareth, or the Jefferson Bible, that contained the teachings of Jesus while removing references to miracles and most elements of the supernatural.
At 23:18 Mills states "This is Bannerman's Island (although the English subtitle incorrectly transcribes her words as 'This is Bannerman Island)". In real life New York, Pollepel Island is in the Hudson River in Duchess County near Cornwall. The principal structure on the island is Bannerman's Castle.