Minimum thermometer

from The Collaborative International Dictionary of English v.0.48

Minimum \Min"i*mum\, n.; pl. {Minima}. [L., fr. minimus. See
   {Minim}.]
   The least quantity assignable, admissible, or possible, in a
   given case; hence, a thing of small consequence; -- opposed
   to {maximum}.
   [1913 Webster]

   {Minimum thermometer}, a thermometer for recording the lowest
      temperature since its last adjustment.
      [1913 Webster]