A Cup of Tea

A Cha' Cuppa translates to 'a cup if tea' in English.

Nan-in was a Japanese Zen Master. 
One day a university professor came to him to understand Zen.

Nan-in seated him and asked for tea to serve him. He poured the cup full and continued pouring. The tea continued spilling over ....

For a while, the professor watched the tea overflowing. But finally said, "Master, the cup if full. The tea has been overflowing."

Nan-in stopped and smiled at professor. He admittingly said, "Like the cup full of tea, you are full of your own thoughts and opinions. If I preach you, you won't be able to gain and retain it. It is necessay that you empty your mind to let Zen enter it."