O, then, I see Queen Mab hath been with you.
She is the fairies’ midwife, and she comes
In shape no bigger than an agate-stone
On the fore-finger of an alderman.
Queen Mab was a tiny fairy who would drive her chariot into the brains of sleeping people and help "give birth" to their dreams. She was a popular figure, inspiring the 1813 Queen Mab: A Philosophical Poem by Percy Bysshe Shelley. In Barrie's earlier work, The Little White Bird (1902), Queen Mab resided in Kensington Gardens and granted Peter Pan his desire to fly again.