In 1881 Francis Edgeworth imagined the hedonimeter:

… let there be granted to the science of pleasure what is granted to the science of energy; to imagine an ideally perfect instrument, a psychophysical machine, continually registering the height of pleasure experienced by an individual, exactly according to the verdict of consciousness, or rather diverging therefrom according to a law of errors. From moment to moment the hedonimeter varies; the delicate index now flickering with the flutter of the passions, now steadied by intellectual activity, low sunk whole hours in the neighbourhood of zero, or momentarily springing up towards infinity. The continually indicated height is registered by photographic or other frictionless apparatus upon a uniformly moving vertical plane …

(David Colander, 2007. Edgeworth’s Hedonimeter and the Quest to Measure Utility. Journal of Economic Perspectives 21 p. 217. JSTOR)

The total happiness or utility experienced would be equal to the sum of the area under the experience graph plotted using such a tool.

However, work carried out by Daniel Kahneman has revealed however that this is not quite how we remember experience. Our remembering self pays more attention to highs and lows and what the end of the experience was like (the peak-end rule), then uses these to turn the whole experience into one ‘prototypical moment’.

If you want to deliver a memorable experience, pay attention to creating high points of good feeling and make sure you deliver a happy ending.