unperceivably

(ˌʌnpəˈsiːvəblɪ)

adv

obsolete imperceptibly

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

References in classic literature ?

In democracies also it is necessary that the rich should be protected, by not permitting their lands to be divided, nor even the produce of them, which in some states is done unperceivably. It would be also better if the people would prevent them when they offer to exhibit a number of unnecessary and yet expensive public entertainments of plays, music, processions, and the like.