From Verinfall Archives
Formula, sometimes called recipes, are the written instructions that describe the process of creating unusual crafted objects, devices, armor and weapons. Commonly associated with Smithing and Tinkering, this might be contain an excerpt of theory/history, an ingredient list and the process for creating the object or effect in question.
In any case, while Formula might appear to simply be a sheet of paper or parchment, casually copying them by route does not impart the copy with the dense information and concepts of the original version. Only with significant effort by someone familiar with the precise craft or academic training can imbue the teaching potential of a Formula to a duplicate.