One bottle is upside down, on top of the other. Fill the top bottle with water, through the hole on the side. Time how long it takes for the water to flow through the caps to the bottom bottle. Adjust the amount of water in the bottle until it takes exactly one minute for the water to flow through [source: Schultz].

These two different methods of timing will nearly always yield different times. Although it is generally acknowledged by professionals that hand measured times are always “faster” than actual or electronic times, there have been few disciplined studies conducted to objectively quantify this difference.

The minute is a unit of time defined as equal to 60 seconds. One hour contains 60 minutes. Although not a unit in the International System of Units (SI), the minute is accepted for use in the SI.