A can of 10 PIBAL (pilot balloon) lights. On the left is a card that turns pink depending on the humidity of the can.
<a href="//commons.wikimedia.org/wiki/User:CambridgeBayWeather" title="User:CambridgeBayWeather">CambridgeBayWeather</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>