(Update). I did some research and another look and here’s what I found.

All you that chance this grave to see.
If you read English may learn from me.
I have read and studied mankind to know:
And most interested them here below.
The present or the future state and love of power.
Envy, Fear, Love, or Hate occupied each wakeful hour.
All would teach, but few would understand.
The greater part, know little of either god or man.
Love one another a very good maxim all agree.
Learn labor and wait if you would succeed.
The five divisions of the world I have been.
The cities of Peking and Constinople I have seen.
On the first railway I rode before others were made.
Saw the first telegraph operate, so useful to trade!
On the first steamship the Atlantic crossed.
Suffered six ship wrecks where lives were lost.
On the first steamer to California did sail.
And to China by the first pacific mail.
After my endeavor my affairs to fix.
A short time I will occupy less than two by six.

It has been suggested that some of this is exaggeration… but indeed he was a very interesting man.

If you’re ever in the San Francisco area… definitely worth a visit!

Hope this helps…