Guidonian hand
In Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. Some form of the device may have been used by Guido of Arezzo, a medieval music theorist who wrote a number of treatises, including one instructing singers in sightreading. The hand occurs in some manuscripts before Guido's time as a tool to find the semitone; it does not have the depicted form until the 12th century. Sigebertus Gemblacensis in 1105–10 did describe Guido using the joints of the hand to aid in teaching his hexachord. The Guidonian hand is closely linked with Guido's new ideas about how to learn music, including the use of hexachords, and the first known Western use of solfege.
Hand cannon
The hand cannon (Chinese: 手銃), also known as the gonne or handgonne, is the first true firearm and the successor of the fire lance. It is the oldest type of small arms as well as the most mechanically simplistic form of metal barrel firearms. Unlike matchlock firearms it requires direct manual external ignition through a touch hole without any form of firing mechanism. It may also be considered a forerunner of the handgun. The hand cannon was widely used in China from the 13th century onward and later throughout Europe in the 14th century until at least the 1560s, when it was supplanted by the matchlock arquebus, which is the first firearm to have a trigger.