Reed level

A reed level is an Arabian invention used for determining the level in construction. It involves creating a hole through a long, straight reed and pouring water into its center. The reed is considered level when the flow of water out of both sides is equal.^[1] This device serves the same purpose as a spirit level.

Water is poured into the center top of the reed grass. The total amount of water, as illustrated by A^(100%), needs to be equally distributed across B₁ and B₂. Equal output at both sides indicates that the reed is horizontally leveled.