As Suggested by Mr. Lavalamp, i went through the Google's Documentation and found the same even after searching the different sites as well. but Talking about Googlebots, they are far more smarter, i think:

Googlebot will not reject a page just because its size is too large, rather it will first crawl Title, URL, Images, headings, Subheadings and Anchor text throughout the page.

This will be probably very less in size and Google can find most of the web page meta data in this document, after that Googlebot can think if more document need to crawl or not, but most of your Web Page resource which are relevant (More) is already Indexed by Google! So one should be careful to Fragment their long Document into pieces of Sections by using headings and subheadings.