心算

Mental \Men"tal\, a. [F., fr. L. mentalis, fr. mens, mentis, the
mind; akin to E. mind. See {Mind}.]
Of or pertaining to the mind; intellectual; as, mental
faculties; mental operations, conditions, or exercise.

What a mental power
This eye shoots forth! --Shak.

{Mental alienation}, insanity.

{Mental arithmetic}, the art or practice of solving
arithmetical problems by mental processes, unassisted by
written figures.