In 1996 scientists in Zurich, Switzerland, built an abacus with individual molecules as beads that all had diameters of less than one nanometer, or one millionth of a millimeter. The beads of the world’s smallest abacus were not moved by a mere finger, but by the ultrafine, conical shaped needle in a scanning tunneling microscope (STM). The scientists succeeded in forming stable rows of ten molecules along steps just one atom high on a copper surface. These steps acted like the earliest form of the abacus (grooves instead of rods to keep the beads in line). Individual molecules were then pushed back and forth in a controlled way by the STM tip, allowing the scientist to manipulate the molecules and “count” from 0 to 10.

There have also been contenders for the world’s largest abacus. In 2001 the Science Museum in London, England, claimed to have the largest at 15.4 feet (4.7 meters) long by 7.2 feet (2.2 meters) wide. Also in 2001, a new contender from Thailand appeared: an 18-foot (5.5 meter) long abacus claiming to be both the world’s biggest abacus and biggest non-electric calculator. It resides in the resort town of Rayong, southeast of Bangkok, and was made by a pharmacist who wanted to calculate drug bills faster than an electronic calculator; the latter claim has been shown to be true, at least by those who can work the abacus with high proficiency, though this was back in 2008, before today’s many gigabyte personal computers and supercomputers (see below).

The people of the ancient Inca civilization of South America used knotted strings called khipus to make mathematical calculations.