Jane Marcet (1769-1858) was the author of early introductory textbooks for children which covered natural philosophy, political economy, chemistry, botany and religion. They were set out as conversations between two pupils, Caroline and Emily, and their schoolmistress, Mrs Bryant, and they successfully condensed complex ideas into an easily grasped form. Many of her books have been digitized and can be accessed here. Readers will notice that, as was typical for the period, no concessions are made to the youth of the audience in terms of vocabulary or the length of the text.
Nine-times-nine, of course, alludes to the multiplication tables which children were expected to learn by rote. However, it also evokes the witches’ speech in Shakespeare’s Macbeth. The first of the weird sisters puts a curse on a sailor, declaring, “Weary se'nnights nine times nine | Shall he dwindle, peak and pine: | Though his bark cannot be lost, | Yet it shall be tempest-tost” (Act 1, Scene 3). Thus the supernatural and baneful permeate what otherwise seems to be a reference to the banalities of the schoolroom.