goldfish keeping _before_ electricity ??

I am curious ... goldfish have been bred and kept for centuries ... 
while most current filtering technologies use electricity ... how did 
the Chinese keep healthy goldfish before electricity?   Any ideas?  I am 
 interested to see what I/we might learn from the traditional aquarist 
methods.

Any references to books/sites, et cetera, would be most appreciated.

BTW, I am familiar with Mike Edwardes' Lotech Tank experience.

Thanks,
Dennis