Let’s Review Classic Ergonomic Seated Posture, also known as Reclined Seating:

The photo shows the body relaxed and the torso upright, the chair is reclined and the back is supported by the chair.

The seat angle allows complete support for the legs to relax, and the stable chair back holds torso in good position.

The thigh-torso angle is shown with the yellow line; here it shows an angle greater than 90 degrees, meaning the torso can lean back with a relaxed angle at the hip

A closer look at the pelvis shows a tangent line from the brim of the pelvis that points relatively close to the base of the head (shown by the angle between the blue lines), meaning the spine is close to the mid-position. The Nachemson and Wilke studies suggest that this seated posture has the lowest lumbar disc pressures.

There is minimal support for the arms, so there is freedom for the hands to move over the keyboard

The position works well for jobs that can be done in reclined postures, like level gaze to the monitor, interviews and meetings, telephone conversations and jobs with minimal forward reach, like dedicated keyboard entry by a skilled typist.

This passive, relaxed posture is easy—and can be sustained for hours. 

To be clear, this is passive, relaxed and reclined seating!