Coud you possibly provide a link to that?
If you check the link from which I copied that info, you will probably find it hot linked from there.
From Heritage Foundation-How many people were in Washington march?:
1.5 million are reported to have passed something called the people meter [just] on Pennsylvania Avenue [alone]
http://www.insideronline.org/blogarchive.cfm?month=9&year=2009#BA311C7A-962A-59E5-2F87892A97FB00CE