singly

Singly, they are every one a representation or appearance of some quality, or other accident of a body without us, which is commonly called an object.

1651, Thomas Hobbes, chapter I, in Leviathan, or The Matter, Forme, & Power of a Common-wealth Ecclesiasticall and Civill, London: […] [William Wilson] for Andrew Crooke, […], →OCLC

Grey-coloured woods covered a large part of the surface. This even tint was indeed broken up by streaks of yellow sand-break in the lower lands, and by many tall trees of the pine family, out-topping the others—some singly, some in clumps […]

1881–1882, Robert Louis Stevenson, “13: How My Shore Adventure Began”, in Treasure Island, London; Paris: Cassell & Company, published 14 November 1883, →OCLC

They dragged themselves from the swamp singly, and in twos and threes, more dead than alive, mere perambulating skeletons, until at last there were thirty of us.

1906, Jack London, chapter XVIII, in Before Adam

Ursula saw that now Bella Watson's chance meetings with him had to be strategically and singly planned by Bella, whose wifely attentions to the bereaved man were markedly meaning.

1907, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Human Toll (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 211