What is the correct preposition to use with "corporation"

Question

I see that both "in" and "at" used with the word corporation. Does it make no difference which one to use or each of this prepositions convey a different meaning?

A couple of real-world examples that use "in":

In the corporation, the boss can still fire you.

Hyatt is renowned in the corporation for his collection of more than 50 horse-drawn carriages.

And a couple that use "at":

From typing up memos at a corporation, to penning blog posts that accompany your online store, to writing grant proposals for your non-profit — it is a skill that will truly come in handy no matter what line of work you end up going into.

The idea started out as a way to keep the best talent at the corporation.

Are "at" and "in" mutually interchangeable in these examples?

P.S. It is clear that we use "in", not "at", for example in the phrase "invest in the corporation". However, in many cases, especially when the word "corporation" answers the question "where?", it is not so clear which preposition should be used. E.g. do a man works in a corporation or at a corporation?

Answer 1

We did the work at the company. [location] We type the memos at the company. [location of memo typing]

at is for location, one cannot stress enough.

Many people in the company were nice. [inside the company]

Hyatt is famous in the company for his x's. [inside the company]

But he is not known outside it.

In companies, bosses can still fire you. [what happens inside a company].

In a company, your boss can fire you.

Answer 2

Formally both are correct.

Though, according to this "in" is preferable, and according to this Ngram only "in" is possible.