Naturalness is perhaps the best guideword to keep in mind.

a mind intent on self-improvement

[W]hilst I was thus musing, and attentively looking upon the Water, to try whether I could discover the Bottom, it happened to me, as it often does to those that gaze too stedfastly on swift Streams, that my Head began to grow giddy, and my Leggs to stagger towards the River, into which questionless I had fell, if Philaretus had not seasonably and obligingly prevented it.

The thieves got away with a million pounds' worth of jewellery.