How to really clear eshell buffer?

[Florian Lindner]

Hello,

I want to really clear an eshell buffer, which means that all former output is 
deleted, not just scrolled away.
eshell/clear only scrolls away, eshell-truncate-buffer also does not clear. 
comint-clear-buffer gives an error message,
probably because eshell is not comint mode.

Thanks,
Florian