Actually it does say a bit more (and leaves it wide open!)
Article 1, Section 2: "The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct. "
I know a lot of people question this, but this is what the government uses to justify more that just number of bodies ... the first census actually also included several questions beyond simply a count. Constitutional Topic: The Census
I read “in such manner...” as the actual methodology rather than questions asked beyond enumeration of live people.
Do they use mail, door to door, smoke signals, make everyone go to the home of their birth, town meetings etc.