The following passage is taken directly from the book:
Again and again students ask, "What is Buddha?" The Masters' seemingly nonsensical responses have survived over the centuries, often as koans.*
What is Buddha?
"Three pounds of flax." - Tung-shan
"Dried poo-poostick." - Yun-men
"This very mind." - Ma-tsu
"Not mind, not Buddha." - Ma-tsu
"What is not the Buddha?" - Nan-yang Hui-chung
"The cat is climbing up the post." - Pa-chiao Hui-ch'ing
"I never knew him." - Nan-yang Hui-chung
"Wait until there is one, for then I will tell you." - Nan-yang Hui-chung
"A new bride rides a donkey, the mother-in-law leads it." - Shou-shan
"When you utter the name of Buddha, wash out your mouth." - Zen saying
"Look within, thou art Buddha." - The Voice of the Silence
*Earlier in the book, there are a couple of pages worth about the koan. Among other things, it says, "Taken from the Japanese ko ("public") and an ("proposition"), the koan can be a question, an excerpt from the sutras, an episode in the life of an ancient Master, a word exchanged in a mondo, or any other fragment of teaching. There are some 1700 traditional koans in existence."