Nan'in Zengu (Jap.)
stories:

Osho
A Bird on the Wing, ch. 1
Zen master:  
Zen disciples:
born:   1834
died:   1904
  
place:  Japan
Note on the Osho story at left:

This tea story is taken from the Paul Reps/Sensaki
book
Zen Flesh Zen Bones, and identifies this
Nan'in as a Japanese Zen master of the Meiji Era
(1868-1912).  This is almost certainly not
accurate, as the anecdote has the distinctive form
of a classical Chinese Tang dynasty era Zen
encounter -- very short, a meeting between a Zen
master and someone else, a unique and
paradoxical set of events, which ends with the
master having the upper hand and the 'someone
else' looking foolish and learning a Zen lesson.

Although not yet able to track down the original
source to this famous Zen story, a few possible
Zen masters using the name with a Japanese
romaji spelling
Nan'in, would be:

Chinese Zen master
Shengshou Nanyin (J. Seiju
Nan'in), a Sichuan based master who lived in the
8th century in southwest China.

There is also another "Nan'in" in Zen history--a
Chinese Chan master
Nanyuan Huiyong, who
lived and taught in 9th century China, and was
also called "Nan'in" in Japanese pronunciation.

And to add to the mix, Osho has related this story
in another set of discourses and has Chinese Zen
master
Nanquan (J. Nansen) as the tea-pouring
sage.

Or maybe it's someone else, who knows? An open
mystery for now it seems.
       oshobob  The Living Workshop                                           
                                               Zen Masters
The Japanese master Nan-in gave audience
to a professor of philosophy.
Serving tea, Nan-in filled his visitor’s cup,
and kept pouring.
The professor watched the overflow
until he could restrain himself no longer:
“Stop!
The cup is overfull, no more will go in.”
Nan-in said,
“Like this cup,
you are full of your own opinions and speculations.
How can I show you Zen
unless you first empty your cup?”

You have come to an even more dangerous
person than Nan-in, because an empty cup won’t
do; the cup has to be broken completely. Even
empty, if you are there, then you are full. Even
emptiness fills you. If you feel that you are empty
you are not empty at all, you are there. Only the
name has changed: now you call yourself
emptiness. The cup won’t do at all; it has to be
broken completely. Only when you are not can the
tea be poured into you, only when you are not is
there no need really to pour the tea into you.
When you are not the whole existence begins
pouring, the whole existence becomes a shower
from every dimension...

                                         --Osho
                         A Bird on the Wing, ch. 1
Chin.: Nanyin
Nan'in (also romanized Nannin), was part of the
Hakuin branch of Rinzai Zen in Japan.