Hand Abacus (14 h 39 m, 21 nov 2018 ano – 14 h 49 m, 1 jul 2019 ano)

Descrição:

The Romans invented the hand abacus it contained several long and short grooves, and had up to five beads in each notch. The Romans developed their hand-abacus as a portable counting board-- the first portable calculating device for both engineers and businessmen.

Adicionado na linha do tempo:

Data: