We have often heard the adaptation of Herodotus’ statement that Egypt is the gift of the Nile. The flooding of the Nile in ancient times was the key to the prosperity of the Nile Valley.
All along the Nile there are still examples of the Nile-o-meters that were used to measure the flooding. The higher the flood water, the more taxes that would be paid into the temple coffers.
In the photo below we see the meter on the Nile at Elephantine Island at Aswan. Notice the water lines along the rock structure. Entrance to the Nile-o-meter is from above, or from the opening to the right of center.
The photo below provides a better view of the Nile-o-meter.
The principle is the same today. We pay taxes based on the amount we have earned within a year.
Therefore one must be in subjection, not only to avoid God’s wrath but also for the sake of conscience. For because of this you also pay taxes, for the authorities are ministers of God, attending to this very thing. Pay to all what is owed to them: taxes to whom taxes are owed, revenue to whom revenue is owed, respect to whom respect is owed, honor to whom honor is owed. (Romans 13:5-7 ESV)