Factual error: In one scene, Winifred asks Gilbert who Trask is and Gilbert replies that Trask is the "mayor", to which Winifred just acknowledges. However, the office of mayor was not created in Massachusetts until 1823, which is 130 years after they were hanged, so given the witch's lack of knowledge of the modern day, she would have likely not known what Gilbert meant.
Factual error: Josephine walks away from her father King Louie 14th, after he tells her she has to marry the young Duke Lintillac for his money. When you look at back of Josephine, you can see a zipper in her skirt. King Louie 14th was King from 1643 until his death in 1715. The first zipper was invented was in 1851. The zipper being used as we know it present day was invented in the early 1890s by Whitcomb L. Judson. (00:55:57)