"Table of Contents" webpart is missing

I was trying to add a "Table of Contents" Webpart to one of my SharePoint page during customization. But i couldn't find it in the web part gallery. I remember i used this webpart in one of my previous project with out any specific steps.

I tried different things to get the webpart in a trial and error manner. At last i was able to get this webpart after activating the "Publishing features".

In my previous project i activated the "Publishing features" for some other purpose, which also added the TOC webpart. So, when i tried to add the TOC webpart it was available right there. I didn't realise it is part of "Publishing features".