Triggers.

Stackhouse, Witch of Endor Raising the Prophet Samuel, 1733

Andrea Immel at the Cotsen Children’s Library has triggers for wonderous dreams ...

Between the ages of four and eight, the young Charles Lamb became “extremely inquisitive about witches and witch-stories” after he went into his father’s “book-closet” and wrestled the two folio volumes of Thomas Stackhouse’s New History of the Bible down from the upper shelf. The physical exertion was repaid by the pleasure of studying the splendid engravings, except for the one which provided the container of his night terrors, which he regretted having ever seen. The plate of the witch of Endor was a trigger: the actual source of the terrors were “archetypes” deep within the mind which “afford some probable insight into our ante-mundane condition, and a peep at least into the shadow-land of pre-existence.”  Samuel was depicted in Stackhouse as a terrible old man wrapped in a mantle, and every night this spectre sent a hag that perched on Charles’ pillow.  He was so frightened that he avoided going into his room even in broad daylight.

Lamb’s memories offer evidence that children did indeed examine large books like Stackhouse which were not specifically intended for children, but neither excluded them because of the wealth of illustrations on subjects they would have learned about elsewhere.  But they are also the earliest of which I am aware which describe accurately and vividly a book illustration that made an indelible impression on a child reader accompanied by a penetrating analysis of its meaning.  

Execupundit with two of the all-time masters.