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Pierre Vallet, Digitalis Purpurea L.

Within the infant rind of this weak flower
Poison hath residence, and medicine power:
For this, being smelt, with that part cheers each part;
Being tasted, slays all senses with the heart.
Two such opposed kings encamp them still
In man as well as herbs, grace and rude will;
And where the worser is predominant,
Full soon the canker death eats up that plant.

W. Shakespeare, Romeo and Juliet, (London, Macmillan and CO., 1932), pp.444-445.