cigars of the beeperThe Incas had no writing systemHmmmn...
But I read from
http://archaeology.about.com/od/qterms/qt/quipu.htm this article:
*************************************************************
Quipu (Khipu, Quipo)
Ancient Writing System of the IncasBy K. Kris HirstThe quipu (also spelled khipu or quipo) is the only known precolumbian writing system in South America--well, perhaps writing system isn't quite the correct phrase. But quipus were clearly an information transmittal system. A quipu is essentially a group of wool and cotton strings tied together. The strings are dyed in many different colors, and they are joined together in many different manners and they have a wide variety and number of knots tied in them. Together the type of wool, the colors, the knots and the joins hold information that was once readable by several South American societies.
Quipus were a tool used by the Inca empire to communicate some kinds of information throughout the Inca Empire. When they arrived in 1532, the Spanish conquistadors viewed the quipu with great suspicion. Thousands of quipus were destroyed in the 16th century. Today there are only roughly 300 quipus which were preserved or have been discovered since that time.
Quipus have not yet been deciphered, but some educated guesses about what they represent have been attempted. Certainly they were used for administrative tracking of tributes. They may have represented maps of the ceque system and/or they may have been mnemonic devices to help oral historians remember ancient legends. They may even have those legends encoded in them; but the likelihood that we'll ever translate them is very small.
Quipus predate the Inca, and are known from the Chimú state. They may have been used by the Moche and Tiwanaku civilizations, although quipu from those societies have not as yet been discovered. The oldest known quipu was discovered at Caral, and dates to about 4600 years ago.
***********************************************************
But still, let us research further. We just can't rely solely from one reference alone.