Engraved jade with a message

The Jade article

In 1975, a jade decorative article was unearthed in China, excavated from the grave of a regional lord some 2500 years ago. The article is now called: Engraved Jade with a Message (行氣玉佩銘).  And on the article, a message on chi-generation was engraved. It clearly indicated such practice was rather common during those days (if it meant to be secretive, it wouldn't be engraved in a piece of decorative article that can be seen by many).

The message reads like this:

“行气，深则蓄，蓄则伸，伸则下，下则定，定则固，固则萌，萌则长，长则退，退则天。天几舂在上；地几舂在下。顺则生；逆则死。”

As is usual with most writings on experiential subjects, in particular those written in classical Chinese, there can be many interpretations. Here is my rendition:

First generate chi, and then store it deep (in one's dantian)
When sufficiently strong, move it downwards
Hold it there (perineum)
Continue till it becomes strong
It will grow
Further extend it outward (to just outside the body)
Then it will retreat (flow back and up - along the whole spinal cord)
And retreat all the way up to heaven (top of the head)
This is the way joining heaven and earth
There is no other way.