Standardizing an Empire

The intricacy of an ancient record-keeping method called a khipu, is capable of representing the precision of  the International System of Units (SI).

Five hundred years ago, how would you keep track of 12 million people spread across some 5,000 kilometers? How would you manage labor or taxation? How would you organize a network of infrastructure, or a capital city? The Inka Empire accomplished all of this with the aid of a brilliant tool: the khipu (or quipu).

Rising to power from 1450-1534 CE, the Andean Empire’s control spanned from present-day Ecuador down to what is now Chile. Known as Tawantinsuyu, or “the four parts together”, the Inka Empire was divided into four regions [Figure 1]. 

Though the Inka have many accomplishments, they are perhaps best known for their impressive engineering. The Inka Road, or Qhapaq Ñan, was the artery of the Empire and allowed for extensive communication and oversight across all four suyus (regions) from Cusco, its capital. Messages, labor, and supplies were sent across the Empire efficiently and easily using these networks. 

Unlike other contemporaneous states and empires, the Inka did not employ a conventional writing system. Instead, the Inka used khipu, a form of record-keeping using colored cords and knots, which was compared to books by Spanish chroniclers at the time.

What is a khipu?

Khipu–meaning “knot” in Quechua–were created from cords typically made of cotton, llama or alpaca fiber. The cords are arranged in a standard structure, consisting of a primary cord that has smaller pendant cords hanging off it. These pendant cords also can have additional cords attached to them called subsidiary cords. There can also be cords which hang in the opposite direction of the pendant cords, called top or summation cords [Figure 2]. It is the pendant cords, subsidiary cords, and top cords that usually contain the knots, though primary cords can contain knots as well. 

The primary cord typically begins with a loop, a knot, or a special bundle called a kayte, with the opposite end trailing off in a long tail that usually does not have any pendant cords attached, sometimes called the “dangle end”. Kayte are thought to indicate the genre of material in a khipu. Scholars “read” the khipu starting from the kayte / loop end and move until they reach the dangle end. The Inka used a base-ten number system, which the knots on the khipu follow, spaced as if each row across the pendant cords of the khipu represents a different decimal place [Figure 3].

Encoding the Khipu

There are many more ways to encode information in a khipu beyond simply tying knots, including the direction the knots are tied with an S or Z twist, the direction of the ply of the cords (S or Z twist), and the ways that the cords are attached to each other (recto or verso) [Figure 4]. 

The colors of khipu cords –and whether a cord is patterned (barber pole, mottled, monochrome, or segmented)– is likely an important source of significance as well [Figure 5].

Some khipu even have patterns across multiple cords (banding or seriation) [Figure 6]. Scholars study all these components to try and gather more meaning from khipu.

Inka Khipu Replica

This cotton Inka khipu displays many elements of signification. The primary cord is mottled and begins with a small kayte, perhaps signaling the khipu genre. Individual pendant cords are either mottled, barber poled, or monochrome, but overall form color bands. This khipu also has a beautiful variety of colors, including green, which is less common than whites or browns. Given the kinks in some of the pendant cords, it appears that some of the knots on this khipu have previously been untied.

Khipu Uses

Khipu were used throughout the Inka Empire, typically by khipukamayuqs (“knot makers”). These khipukamayuqs were responsible for the recording and reading of khipu, and employed these devices to keep the Empire running. The khipu were used to record many different types of information–which have been documented by several Spanish chroniclers during the colonial period–such as census data, tributary accounting, resource inventory, and perhaps even histories and lyrical narratives. Khipu could even be wrapped into small portable bundles and carried across the empire by official messengers, or chaskis. In the 17th century, Guaman Poma de Ayala, an Indigenous chronicler from colonial Peru, depicted both khipukamayuqs and chaskis in his drawings [Figure 7 & Figure 8].

International System of Units (SI) Khipu

The seven units of the International System of Units (SI), also known as the metric system, are represented on the SI khipu. The SI Khipu was created by George Washington University archaeologist Jeffrey Splitstoser.

This object transcends Inka conventions of khipu making to creatively represent these units of measurement in several ways, including the use of wrapped colors to indicate which pendant cord represents which SI unit; the representation of decimals; a signifier for zero; and a knot type to indicate the integer powers of ten.

The primary cord is also barber poled with the seven colors associated with the seven SI units. 

Each SI pendent cord is detailed in the diagrams below:

Visit the ‘Defining the International System of Units (SI)’ exhibit online or in NIST Museum for the definitions of each unit.

This exhibit is a collaboration with the Dumbarton Oaks Museum and the Association of NIST Hispanic Americans.

Example of how to reference this exhibit:
NIST Museum. 2023. Standardizing an Empire. Gaithersburg, MD: National Institute of Standards and Technology. Online. https://www.nist.gov/nist-museum/standardizing-empire

Author. Year. Exhibit Name. Place published: Publisher. Online. URL.