Railway apparatus name

Hi,
I'm hoping that someone here will be able to help me. I'm interested to know the name of the specific piece of railway apparatus which I'm about to describe.
I think it's obsolete now, but in the early 1900's and perhaps before, it was used for track inspection and other maintainence type stuff.
It's a small, single carriage with a lever device on top. The lever is like a see-saw, and as it is pushed up and down by hand, the carriage moves along the track.
If anyone knows what these are called, I'd appreciate if they could e-mail me at dogplatter.enterprises@gmail.com, or reply to this particular thread.
Thanks in advance.