The earliest scrap of paper still in existence, a crude material made mostly from hemp fiber found in a tomb in China in 1957, dates back to sometime between 140 and 87 B.C. But Cai Lun, a eunuch in the Han court in A.D. 105, is credited as the inventor of the first really high-quality writing paper, which he fashioned by crushing and combining tree bark, hemp, linen rags, and scraps from fishing nets and then treating the mixture with lye to break it down into finer fibers, according to Li Shi’s book The History of Science and Technology in the Qin and Han Dynasty.

“Administrative documents continued to be written on boards of wood and slips of bamboo for several centuries—they preserved better, perhaps,” Yates explains. But after the collapse of the dynasty, Cai Lun’s improved paper came into its own.

According to Robert Temple’s highly-regarded history of Chinese inventions, The Genius of China, the Han Dynasty saw the development of the suspension bridge, a flat roadway suspended from cables, which probably evolved from simple rope bridges developed to span small gorges. But by A.D. 90, Han engineers were building more sophisticated structures with wooden planks.

Han Dynasty salt miners in the First Century B.C. were the first to build derricks and use cast iron drill bits to dig holes as deep as 4,800 feet into the Earth in search of brine, which they would extract from below with tubes, according to Temple’s book. The technique they developed was the forerunner of modern oil and gas exploration.

The wheelbarrow was developed in China perhaps as early as 100 B.C, according to this 1994 article by M.J.T. Lewis in the journal T_echnology and Culture_.

Zhang Heng, an early Chinese scientist, explored fields ranging from astronomy to clock-making. But he’s probably best known for creating the first device for detecting distant earthquakes, which he introduced to the Han court in A.D. 132 Its design was simple—an urn equipped with a pendulum.

When it picked up a vibration, it dropped a ball from the mouth of a metal dragon into a metal frog, creating a loud clang. The first time that happened, nobody in the court reportedly felt anything, but a few days later, a messenger from a village 400 miles away arrived to inform the emperor that an earthquake had occurred there.

Right around the beginning of the Han Dynasty in the early 200s B.C., Chinese metallurgists built the first blast furnaces, which pumped a blast of air into a heated batch of iron ore to produce cast iron, according to Chinese technology historian Donald B. Wagner.

According to Temple, the First Century B.C. Chinese used a tool somewhat similar to the one used by plumbers and tinkerers, in which a sliding caliper gauge allowed the pieces to be adjusted. (Modern wrenches have a worm screw, a different mechanism, but the function is the same.) Initially, the devices seem to have been used for measuring, rather than loosening and tightening lug nuts or pipes.

According to Robert Greenburger’s book The Technology of Ancient China, the Chinese were using iron plows to till farm fields as far back as the 6th Century B.C. But a couple of hundred years later, some ingenious Han inventor came up with the kuan, also known as the moldboard plow. The tool had a central piece that ended in a sharp point, and wings to push the soil away and reduce the friction. The new plow helped the Chinese practice contour plowing, in which they followed the shapes of the hills, to reduce soil erosion.

Ancient horsemen had to let their legs dangle as they rode, though the Romans rigged a hand-hold on saddles to help them stay on the horse when things got rough. A Han Dynasty inventor made things a lot easier by making cast iron or bronze devices that a rider could slip his foot into, according to Temple. It was such a revolutionary invention that it spread over the next several centuries across Asia to Europe, where it made it possible for medieval knights to ride their steeds in heavy armor without tumbling off.

The Chinese developed the device for steering a ship in the First Century A.D., according to Chinese technology historian Yongxiang Lu.

The rudder enabled ships to steer without using oars, making it a lot easier to navigate. According to Temple’s book. the invention took about millennium to reach the west, where it helped Christopher Columbus and other explorers navigate the ocean.