what is the difference between on, in or at a meeting?

what is the difference between the following sentence:

1, He is in a meeting.

2, He is at a meeting.

3, He is on a meeting.

I have found that the difference between first 2 sentences is in a meeting implies being on the same premises as the speaker, but at a meeting implies being on a different premises than the speaker..

But I did find any information about on a meeting or on the meeting on google, however, I found there are 380 records about on a meeting and 880 records about on the meeting on http://corpus.byu.edu/now/, and although some of those records are not what I’m asking.

So, I want to know if we can use the preposition on in front meeting? And if so, what is the difference between the 3 sentences?