Booting root filesystem from usb device

[Ezequiel García]

Hi, 

I have a very silly question. I was building a small hand made root
filesystem (with busybox and such) just to show how the process would be 
done.

Something pretty similar to free-electrons 'embedded linux from scratch' (http://free-electrons.com/docs/elfs/) but on a usb device (pen-drive).
So, I put me kernel, busybox and stuff and installed lilo onto the mbr.

The problem is when the kernels boots it can't find the usb partition (sdc1)
to mount (i.e. the root device). 

I know the usual way to do this is using initrd or similar, 
but I don't want to get that into the equation since the 
whole project is just for educational purposes and 
I want to keep things as simple as possible.

Ezequiel.