  We present an engaging levitation experiment that students can perform at
home or in a simple laboratory using everyday objects. A cork, modified to be
slightly denser than water, is placed in a jug containing tap water and coarse
kitchen salt delivered at the bottom without stirring. The salt gradually
diffuses and determines a stable density stratification of water, the bottom
layers being denser than the top ones. During the dissolution of salt, the cork
slowly rises at an increasing height, where at any instant its density is
balanced by that of the surrounding water. If the cork is gently pushed off its
temporary equilibrium position, it experiences a restoring force and starts to
oscillate. Students can perform many different measurements of the phenomena
involved and tackle non-trivial physical issues related to the behaviour of a
macroscopic body immersed in a stratified fluid. Despite its simplicity, this
experiment allows to introduce various theoretical concepts of relevance for
the physics of the atmosphere and stars and offers students the opportunity of
getting acquainted with a simple system that can serve as a model to understand
complex phenomena such as oscillations at the Brunt-V\"{a}is\"{a}l\"{a}
frequency and the propagation of internal gravity waves in a stratified medium.
