A important book for me in my university days, was by Alan Watts- The Way of Zen.
All my life I have been able to recite the poems quoted in this book about the Zen idea of mindfulness

How many legs?

The centipede was happy quite
Until a toad in fun, said
Pray which leg goes after which
Which worked his mind to such a pitch
Considering how to run

(Page 47 The Way of Zen)