Walter Alison Phillips, 1911 Encyclopædia Britannica, Volume 7… (1911)
“ The substitution of the cope for the chasuble in many of the functions for which the latter had been formerly used was primarily due to the comparative convenience of a vestment opened at the front, and so leaving the arms free. A natural conservatism preserved the chasuble, which by the 9th century had acquired a symbolical significance, as the vestment proper to the celebration of Mass ”
