Before the advent of money, barter was the accepted means of payment where anything could serve as "currency." Here's a brief tour through the quirkier side of currency history. Funny money, indeed.
In Micronesia on the island of Yap, the Rai stone is legal tender and heavy at that. The coins are rather large circular limestones with a hole in the center. At between five and 20 feet in diameter, these numismatic colossi derive their value not from monetary or fiscal policy, but rather from their size, weight and effort to transport.
In parts of West Africa up until the 20th century, twisted iron barbs with a spatula at one end and a T at the other were used to transact business, though they look more like a steel leader on a fishing line. Known as Kissi money, broken pieces of it were deemed worthless unless restored in ceremonial fashion by a witchdoctor, in a case of currency rebasement.
The Canadian $1 million coin weighs approximately 220 pounds, most of which is comprised of gold bullion, and sells for roughly twice its face value due to the high value of its content. Don't plan on paying for sundry items with this. You'll empty the vendor's till and everything in the bank.
The ancient south Indian Vijayanagara Empire lays claim to the smallest coin in numismatic history. The quarter silver Tara weighs .06 ounces and measures four millimeters in diameter.
Extensively used in East Africa and in the Sahara desert centuries ago, salt is one of the oldest forms of payment in the world, harking back to the barter system. Turmeric spice wrapped in coconut fibers seems more like something you'd see used on the Food Channel, but in the Solomon Islands it passes for currency. In Central America and Mexico, cocoa beans were a delectable form of payment.
Unlike the late 1990s magazine advertisement glorifying the fermented curd, at one time the phrase could be taken quite literally. Parmigiano Reggiano had been a currency and accepted bank collateral in Italy. In Burma poisonous money seeds were used as a means of exchange at one time and nothing else, lest it be the last time.
Light in weight, but heavy in value, cashmere is the prized export from Mongolia. Yet in 2007, the north Asian nation produced a unique 500 Tugrik coin with the likeness of former U.S. president John F. Kennedy on one side and equipped with a button that enables the holder to listen to a sound bite from his famous 1961 "Ich bin ein Berliner" speech.
After the overthrow of Joseph Mobutu Sese Seko in what is now the Congo (formerly Zaire), the successor Congolese government removed his face from the existing currency rather than print new bills. Palau in 2007 issued a silver dollar with the likeness of the Virgin Mary and an embedded vial containing holy water from Lourdes, France. And around 50 million Chilean pesos in 2008 were minted with the misspelled "Republica de Chiie."
No romp through the world of money would be complete without a brief mention of some regional forms of currency specific to certain parts of the world and unique to certain times in history. Numerous towns and cities across America use region-specific scrip ostensibly to support the local economy and insulate it from a global economic meltdown. Examples include Berkshares, Bay Bucks, Ithaca Hours and Potomacs.
A function of history: occupying governments issued money that circulated in the regions that they controlled. Examples would include military yen notes issued by the Japanese in the occupied regions of Manchuria (Manchukuo), the Philippines and Hong Kong; 100 Kronen coins issued in Soviet occupied Czechoslovakia in 1949 with a profile of Josef Stalin; and military currency used by the German army in occupied Channel Islands. Vietnamese Green Stamp money were notes with detachable coupons exchangeable for specific items only (e.g. coupons for specific items of clothing which were not fungible).
Money is perceived to have value if it can be used to purchase goods and services. As you have read, its form and denomination are very much a function of the culture and circumstances in which it exists.