The superscription consists of the sign The Superscription 1376 which consists of the letter R with an oblique dash across the final stroke. The letter R is an abbreviation for the Latin word Recipe, meaning take or take thou; so it instructs the pharmacist to take of the ingredients mentioned below the amounts specified. The oblique dash across the final stroke of the R probably is derived from the old symbol % which represented a prayer to Jupiter. It was the custom of the old Roman physicians to begin a prescription with this invocation to their God of Gods to bless the remedies. The theory as to the origin is strengthened by the fact that the early Christian physicians used, instead of it, the cross. The letter R and the symbol 4 are very well represented by our present sign

Another theory is based on the claim that the oblique line was used by the Romans much as we use the period, and that in this instance it has no other meaning.