At address formation Instagram posts have a typical pattern:
https://www.instagram.com/p/SYMBOLS/"/p/" means "post ”. But instead of “CHARACTERS” there is usually a long string.
But for the first posts in the history of instagram, this is not even a line, but single characters. The first surviving post under the letter “C”:
https://www.instagram.com/p/C/
In the photo, Instagram co-founder Kevin Systrom takes a picture of a dog with the comment “test”.
If you wish, see the rest photos in the order of publication (2, 3, etc.), you can replace the letter with the next one in the alphabet. For example “D”, “E” and so on.