Ciamician in 1908 described the first stereospecific photochemical reaction irradiating a natural occurring chiral terpene, carvone. Ciamician proposed a structure for the obtained photoisomeric product without a study devoted to confirming it. Some year later, Sernagiotto proposed, on the basis of some incomplete experimental results, a new structure for the photoisomer. Büchi proposed, on the basis of other experimental but not conclusive results, to return to the structure proposed by Ciamician. Finally, NMR spectrum of the photoisomer, performed in 1965, confirmed the Ciamician structure.