In doing some research on friendship for a paper I'm writing, I came across this fine quote from Emerson:
Do not mix waters too much. The best mix as ill as good and bad. You shall have very useful and cheering discourse at several times with two several men, but let all three of you come together and you shall not have one new and hearty word. Two may talk and one may hear, but three cannot take part in a conversation of the most sincere and searching sort. In good company there is never such discourse between two, across the table, as takes place when you leave them alone. In good company the individuals merge their egotism into a social soul exactly co-extensive with the several consciousnesses there present. No partialities of friend to friend, no fondnesses of brother to sister, of wife to husband, are there pertinent, but quite otherwise. Only he may then speak who can sail on the common thought of the party, and not poorly limited to his own. Now this convention, which good sense demands, destroys the high freedom of great conversation, which requires an absolute running of two souls into one.
By the way, don't conclude from Emerson's use of the word "men" that he was a male chauvinist; in fact, two of his closest friends, whom he valued deeply for their acumen and insights, were Margaret Fuller and Caroline Sturgis.