How to Maintain a Relationship, 15th century
Walters Art Museum MS W.166, f. 118r
If a woman places feathers from a capon that has hatched young chickens in her husband’s ear as well as hair from the right leg of his dog and from the tip of his cat’s tail, he would never forget his love for her.
The Distaff Gospels (trans. Madeleine Jeay & Kathleen Garay)
The secret to a lasting relationship: just empty the vacuum cleaner in your partner’s ear and you’ll live happily ever after.
As a capon is a castrated cockerel that would be a neat trick.
the real trick was hatching chickens in her husband's ear.
It probably means a capon that sat on eggs and hatched them, not one that laid eggs.