In 18th- and 19th-century German philosophy, a Zeitgeist is an invisible agent, force or Daemon dominating the characteristics of a given epoch in world history. The term is usually associated with Georg W. F. Hegel, contrasting with Hegel's use of Volksgeist "national spirit" and Weltgeist "world-spirit"
Google now states a definition of Zeitgeist to be: "the defining spirit or mood of a particular period of history as shown by the ideas and beliefs of the time."
This is the first of these particular containers that I've hidden, so it's not particularly zeitgeistian just yet. The cache is a 50ml container, hanging from a branch of a tree. A pencil is included in the cache.