Lettuce, greens and celery, though much eaten, are worse than cabbage, being equally indigestible without the addition of condiments. Besides, the lettuce contains narcotic properties. It is said of Galen, that he used to obtain from a head of it, eaten on going to bed, all the good effects of a dose of opium.

The Young House-keeper: Or, Thoughts on Food and Cookery (ed. 1838)