(R)‐(+)‐Pulegone is a monocyclic monoterpene ketone and main constituent of the essential oil of pennyroyal. The elucidation of its structure in the steps molecular formula, constitution and absolute configuration from 1891–1929 is reported. Formerly, pennyroyal was used as panacea, spice and to repell fleas from the body. Today, incorporation of pulegone should be avoided as pulegone forms toxic metabolites. However, pennyroyal oil, easily available as essential oil by steam distillation, is an appreciated source of (R)‐(+)‐pulegone. (R)‐(+)‐Pulegone is a valuable enantiopure building block from nature's chiral pool which is used for the synthesis of other chiral compounds. Pulegone is a good example for spectroscopic interpretations. To this end, all spectra are presented. Based on a Bachelor thesis this project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).