What was in the letter to the Dursleys Dumbledore left with baby Harry?
What did the Howler to Aunt Petunia in Order of the Phoenix mean? is related to this question, but it is not the same question. The answer to the first question is that Dumbledore sends Petunia a Howler, telling her to remember his last letter, which is the letter he left with Harry as an infant. I am asking what was in the letter left with baby Harry? I could not find this question when I did my due diligence; I hope it is not a duplicate.
Is there any information about this? In Order of the Phoenix, Vernon attempts to throw Harry out of the house following the dementor attack on Harry and Dudley, and Dumbledore sends a Howler:
‘You can open it if you like,’ said Harry, ‘but I’ll hear what it says anyway. That’s a Howler. [SNIP] Open it!’ Harry urged her. ‘Get it over with! It’ll happen anyway.’
Aunt Petunia’s hand was trembling. She looked wildly around the kitchen as though looking for an escape route, but too late – the envelope burst into flames. Aunt Petunia screamed and dropped it.
An awful voice filled the kitchen, echoing in the confined space, issuing from the burning letter on the table.
‘Remember my last, Petunia.’
Order of the Phoenix - page 40-41 - Bloomsbury - chapter two, A Peck of Owls
What was in that last letter? I feel sure this has been addressed, but I cannot find it. What did Dumbledore write to the Dursleys that convinced such awful people to take in and care for (take that with a grain of salt) a hated and unwanted relative?