well he thinks like an extortionist
"Mention extortion again, and I'll have your legs broken."
Harvard offered little more than 10 cents on the appraised dollar for his property!!!!!
How about you sell me your property for 10% of the value???
Agreed. The threat to burn them is extortion. Legal extortion, since he owns them, but burning them would be a crime against history.
One issue here us that there are two parts to the value of the papers. One is that they are verifiable physical originals. The other is that they contain unknown (?) content. Once the content is known, they really just become prestige pieces for a collection.
If I were him I wouldnt burn them but rather threaten to auction the things slowly, one at a time.