principally

The game principally consists in taking and carrying off the ball from the opposite party, after being hurled into the air midway between two high pillars, which are the goasl, and the party who bears off the ball to their pillar, wins the game[…]

1828, Elizabeth Elkins Sanders, Conversations Principally on the Aborigines of North America, Salem: W. and S. B. Ives, page 65

Timber, hides, furs, and minerals from the north, and grain and other products from the south and the immediate vicinity of the town itself are brought, principally by river, to this point, where the railway cuts the great central waterway of Siberia.

1916 May 28, M[aria] A[ntonina] Czaplicka, “A Year in Arctic Sibera”, in The Wide World Magazine, volume 37, number 217, page 54

When asked to guess whether champagnes they were drinking was made principally from white or black grapes, most tasters including wine writers and journalists were unable to tell the difference.

2013 November 29, Nick Collins, “Even Champagne experts blind to grape varieties”, in The Telegraph