unsight unseen

It seems the general of the Tartars, after having laid siege to a strong town in China, and taken it by storm, would set to sale all the women that were found in it. Accordingly he put each of them into a sack, and, after having thoroughly considered the value of the woman who was enclosed, marked the price that was demanded for her upon the sack. There was a great confluence of chapmen, that resorted from every part, with a design to purchase, which they were to do 'unsight unseen.'

1712 October 16, Joseph Addison, “On Seducers—Procuresses—Letter from one”, in The Spectator, number 511, quoted in The Works of Joseph Addison, volume 2, page 274, published 1842

Their new Chaps were so eager, that they would have bargain'd with the old Captain before-hand: Nay Friend, said he, I will not trade with thee unsight and unseen; neither do I know whether the Master of the Sloop may not have sold his Loading already to some Merchants of Salset; but if he has not, when I come to him, I think to bring him up to thee.

1720, Daniel Defoe, Captain Singleton, page 311