How was a meter defined in 1791?

In the eighteenth century, there were two favoured approaches to the definition of the meter. One approach suggested that the metre be defined as the length of a 'seconds pendulum' (pendulum with a half-period of one second). Another suggestion was defining the metre as one ten-millionth of the length of the Earth's meridian along a quadrant (the distance from the Equator to the North Pole).

In 1791, the French Academy of Sciences selected the latter definition (the one related to Earth's meridian) over the former (the one with the pendulum) because the force of gravity varies slightly over the surface of the Earth's surface, which affects the period of a pendulum.