尺牍

尺牘
chǐdú
(literary) a one-foot-long strip of wood or bamboo, used for writing in ancient times; (as a metonym) letter; written message

CEDICT

literary

Entry Composition

1 尺 chǐ
  1. a Chinese foot
  2. one-third of a meter
  3. a ruler
  4. a tape-measure
  5. one of the three acupoints for measuring pulse in Chinese medicine

classifiers: 支, 把
2 牍 dú documents