From The Black Cauldron by Lloyd Alexander in The Chronicles of Prydain, Book 2, Chapter 14 (“The Price”):
“You make sport of us,” Taran cried angrily. “The price you ask is beyond what any of us can pay.”
Orddu hesitated. “Possibly you’re right,” she admitted. “Well, then, something a little more personal. I have it!” she said, beaming at Taran. “Give us—give us the nicest summer day you can remember! You can’t say that’s hard, since it belongs to you!”
“Yes,” Orwen said eagerly. “A lovely summer afternoon full of sunlight and sleepy scents.”
“There’s nothing so sweet,” murmured Orgoch, sucking a tooth, “as a tender young lamb’s summer afternoon.”
“How can I give you that?” protested Taran. “Or any other day, when they’re—they’re inside of me somewhere? You can’t get them out! I mean…”
“We could try,” Orgoch muttered.