Body parts as early units, why they failed, and old Indian measures
People first measured with body parts such as the hand span and cubit. These changed from person to person, so rulers fixed standards, and India had its own systems.
Body parts and other early units
| Unit | What it was |
|---|---|
| Digit | Width of one finger |
| Hand span | Tip of the thumb to the tip of the little finger, hand fully stretched |
| Foot | Length of a human foot |
| Cubit | Elbow to the tip of the middle finger |
| Fathom | Distance between the finger tips of both arms stretched out sideways |
| Pace | One stride of a Roman soldier, that is two steps (left and right); 1000 paces made a mile |
| Grain | Mass of one wheat grain, a unit of mass in the 1500s |
Activity: measure with your hand span and compare
Do this with 4 or 5 family members or friends.
- 1Choose a long object, such as a table, a bed or a door.
- 2Measure its length with your hand span. Count whole spans, then the leftover in finger widths (digits).
- 3Write your result in a table, for example '6 spans and 2 digits'.
- 4Ask each person to measure the same object in the same way, and record their results.
- 5Compare the results.Observe: the numbers differ, because each person's hand is a different size.
- 6★Conclude: body parts cannot give accurate, repeatable measurements.
★ key step
From body units to fixed standards
The fix was to choose one agreed length and copy it. About 3000 BC, the Egyptians fixed a standard cubit from the forearm of their ruler, the Pharaoh. Measuring sticks of exactly that length were made, so the cubit was the same all over Egypt. In England, King Henry I fixed the yard as the distance from his nose to his thumb, with the arm stretched out. Queen Elizabeth I fixed the mile as 8 furlongs. A furlong (220 yards) was how far a pair of oxen ploughed without a rest. But each standard lasted only while its ruler ruled, and each country had its own. By the 1700s, far too many different units were in use.
Old Indian measures
| Period | What was measured and how |
|---|---|
| Ancient times | Time of day from the length of shadows; long periods by the cycle of the Moon (lunar months) |
| Harappan (Mohenjodaro), about 5000 years ago | Bricks across the region had the same shape: length : breadth : height = 4 : 2 : 1 |
| Mauryan (Chandragupta Maurya), about 2400 years ago | The state made everyone use the same weights and measures. Smallest length: parmanu; small lengths: angul; long distances: yojan (about 10 km in your NIOS lesson). Listed in Kautilya's Arthashastra |
| Ayurveda | Fixed units of mass and volume, so the right dose of medicine was given |
| Mughal (Akbar) | The gaz for length, divided into 24 tassuj; used for land, buildings, wells and roads, and still heard in villages |
| British period, till 1947 | Inch, foot and yard for length; grain, ounce and pound for mass; Indian mass units ratti, masha, tola, chhatank, seer and maund |
Old Indian units of mass (British period)
Worked example: how many ratti make a tola?
Using the table, how many ratti make 1 tola? If 1 ratti is about 120 mg, what is the mass of 1 tola in grams?
- 1 tola = 12 masha.
- 1 masha = 8 ratti, so 1 tola = 12 × 8 = 96 ratti.
- Mass of 1 tola = 96 × 120 mg = 11 520 mg.
- 11 520 mg ÷ 1000 = 11.52 g, about 11.5 g.
96 ratti; about 11.5 g, using the rounded value of 120 mg for a ratti (the official tola was later fixed at about 11.66 g)
Many goldsmiths in India still quote gold by the tola, and some villagers still measure land in gaz. The old units live on beside the metric system.
2 marks: “Why can parts of the human body not be used as units for accurate measurement? Give two examples of such units.” Body parts differ in size from person to person, so results differ and cannot be repeated. Examples: hand span and cubit (also foot, digit and fathom).
2 marks: “Match each unit with the period in which it was used: (i) gaz (ii) yojan.” (i) Gaz: the Mughal period, under Akbar. (ii) Yojan: the Mauryan period, under Chandragupta Maurya, for long distances.
1 marks: “What ratio did the bricks of Mohenjodaro follow?” Length : breadth : height = 4 : 2 : 1, the same everywhere.
Body units vary; standards stay. Maurya: parmanu to yojan. Akbar: a gaz of 24 tassuj.