In ancient Ireland, the Celts had "Houses of Memory," which Caitlin Matthews describes as quiet, dark huts with only a few flickering candles. In these abodes of imagination an aspiring poet would sometimes be assigned a subject to ponder. The student would be in the dark, undisturbed for many hours. Sometimes a stone would be placed on the poet's chest to ensure lack of movement. Within this incubation chamber, imagination would flourish.
— William John Fitzgerald in Blessings for the Fast Paced & Cyberspaced