From The Collaborative International Dictionary of English v.0.48:
Sadness \Sad"ness\, n. 1. Heaviness; firmness. [Obs.] [1913 Webster]
2. Seriousness; gravity; discretion. [Obs.] [1913 Webster]
Her sadness and her benignity. --Chaucer. [1913 Webster]
3. Quality of being sad, or unhappy; gloominess; sorrowfulness; dejection. [1913 Webster]
Dim sadness did not spare That time celestial visages. --Milton. [1913 Webster]
Syn: Sorrow; heaviness; dejection. See Grief. [1913 Webster]