fiducial
adjective
accepted as a fixed basis of reference or comparison.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The adverb "fiducially" first brought to my notice, as the synonym of confidently, steadily.
From Personal Memoirs of a Residence of Thirty Years with the Indian Tribes on the American Frontiers by Henry Rowe Schoolcraft