It's hard to pinpoint the absolute earliest measuring device, as early humans likely used natural objects and their own bodies for estimation long before formal tools were developed. However, some of the earliest known dedicated measuring devices include:

* Ancient Egyptian cubit sticks (c. 3000 BCE): These were simple sticks with a specific length (about 52.5 cm) representing a unit of measurement called the cubit, used for building and surveying.

* Sundial (c. 3500 BCE): Ancient Egyptians developed sundials to measure time by the shadow cast by a vertical stick.

* Water clocks (c. 1500 BCE): Water clocks were used in ancient Egypt and Mesopotamia to measure time by the rate of water flow.

* Sand timers (c. 1500 BCE): These were similar to water clocks, using sand instead of water to mark time intervals.

* Measuring vessels (c. 2000 BCE): Ancient civilizations used standardized vessels with specific volumes, like jars and jugs, for measuring liquids.

It's important to note that this list is not exhaustive and there were likely other rudimentary measuring devices in use during these ancient periods. These early devices paved the way for the more sophisticated measuring instruments we use today.