- AD 77–79, Gaius Plinius Secundus (author), Karl Friedrich Theodor Mayhoff (editor), Naturalis Historia (1906), book XV, chapter xxviii:
- nec non et honor iis naturae peculiaris gemino protectis operimento, pulvinati primum calycis, mox lignei putaminis.
- Nature, too, has conferred upon it a peculiar honour, in protecting it with a two-fold covering, the first of which forms a hollowed cushion for it to rest upon, and the second is a woody shell. ― translation from: John Bostock and Henry Thomas Riley, The Natural History (1855), book XV: “The Natural History of the Fruit-trees”, chapter xxiv (xxii): ‘Nine Varieties of the Nut’
