What do you mean by seller must pass Satoshi text? At sych amount that wrote you need to use the OTC service provided by a crypto exchange. Since your account is brand new I don't think anyone would trust you here. Moreover those who have that value of Bitcoin will never sell it as they know the potential of Bitcoin.
Maybe he's talking about signing a signature to prove that you have the coins in your wallet but I wouldn't believe the OP since he's a newbie and amd mightn't be serious. If I have the amount of money the OP is claiming to have and I want to buy Bitcoin, I'll just register on a trusted exchange to buy the Bitcoin from them. I will have a security of not getting scammed as I can't trust any random individual on the internet with that amount of money. There are many trusted exchanges that will have that quality of Bitcoin to buy.
To avoid suspicious I can deposited the money small quantity at a time and also withdrawal small quality of Bitcoin until I have been able to withdraw everything from the exchange as large quality of transaction can be flagged and I'll need to provide more verification but I would not want to add extra KYC after the usual documents that they'll need to make me eligible to buy and withdraw some Bitcoin from the exchange.