Short History of Financial Euphoria by John Kenneth Galbraith, Harvard, 1990

This process, once it is recognized, is clearly evident, and especially so after the fact. There are those who are persuaded that some new price-enhancing circumstance is in control, and they expect the market to stay up and go up, perhaps indefinitely. It is adjusting to a new situation, a new world of greatly, even infinitely increasing returns and resulting values. Then there are those, superficially more astute and generally fewer in number, who perceive or believe themselves to perceive the speculative mood of the moment. They are in to ride the upward wave; their particular genius, they are convinced, will allow them to get out before the speculation runs it course. They will get the maximum reward from the increase as it continues; they well be out before the eventual fall.

The Great Crash 1929 by John Kenneth Galbraith, Harvard, 1954

In the autumn of 1929, the mightiest of Americans were, for a brief time, revealed as human beings. Like most humans, most of the time, they did some very foolish things. On the whole, the greater the earlier reputation for omniscience, the more serene the previous idiocy, the greater the foolishness now exposed. Things that in other times were concealed by a heavy facade of dignity now stood exposed, for the panic suddenly, almost obscenely, snatched this facade away.