The homunculus ("little man") is an alchemical claim rather than a folk creature, and it has a datable text. The treatise De Natura Rerum, circulated under the name of Paracelsus (early sixteenth century), gives a recipe: human seed sealed in a vessel and putrefied in horse dung for forty days until something transparent and man-shaped stirs, then nourished daily with human blood and kept at the warmth of a mare's womb for forty weeks, whereupon a living, tiny, well-formed child is said to result, which will teach its maker every art.
The idea sits within a wider early-modern debate about generation, and it is often linked to preformationism, the theory that a fully formed miniature organism is already present in the seed or egg, which some illustrators drew as a tiny man in the sperm. As a figure the homunculus passed into literature, most famously in Goethe's Faust, Part Two, where the alchemist Wagner produces a luminous spirit-child in a flask, and into twentieth-century psychology, where C. G. Jung read the alchemists' talk of making an artificial man as a symbolic account of inner transformation rather than a laboratory procedure.