The following quotes are from "The Case for Flexible Exchange Rates" by Milton Friedman, published in Friedman's Essays in Positive Economics, University of Chicago Press, 1953.
From page 165:
If internal prices were as flexible as exchange rates, it would make little economic difference whether adjustments were brought about by changes in exchange rates or equivalent changes in internal prices. But this condition is clearly not fulfilled. The exchange rate is potentially flexible in the absence of administrative action to freeze it. At least in the modern world, internal prices are highly inflexible. They are more flexible upward that downward, but even on the upswing all prices are not equally flexible. The inflexibility of prices, or different degrees of flexibility, means a distortion of adjustments in response to changes in external conditions. The adjustment taes the form primarily of price changes in some sectors, primarily of output changes in others.
Wage rates tend to be among the less flexible prices. In consequence, an incipient deficit that is countered by a policy of permitting or forcing prices to decline is likely to produce unemployment rather than, or in addition to, wage decreases. The consequent decline in real income reduces domestic demand for foreign goods and thus demand for foreign currency with which to purchase these goods. In this way it offsets the incipient deficit. But this is clearly a highly efficient method of adjusting to external changes. If the external changes are deep-seated and persistent, the unemployment produces steady downward pressure on prices and wages, and the adjustment will not have been completed until the deflation has run its sorry course.
From page 173:
The argument for a flexible exchange rate is, strange to say, very nearly identical with the argument for daylight savings time. Isn't it absurd to change the clock in summer when exactly the same result could be achieved by having each individual change his habits? All that is required is that everyone decide to come to his office an hour earlier, have lunch an hour earlier, etc. But obviously it is much simpler to change the clock that guides all than to have each individual separately change his pattern of reaction to the clock, even though all want to do so. The situation is exactly the same in the exchange market. It is far simpler to allow one price to change, namely, the price of foreign exchange, than to rely upon changes in the multitude of prices that together constitute the internal price structure.