How to cast shadow on an invisible plane

Unity Engine
1

I have switched the mesh renderer off a plane because I want it to be invisible but I would still like to cast shadows onto it.

Is there anyway to do this easily?

2

Aparently the post here by Kragh acheives what you want, though i havent tested it
http://forum.unity3d.com/threads/14438-Matte-Shadow?highlight=matte+shadow