Asa moved to Ontario in large part due to his father-in-law, Col. William Marsh, who was a loyalist.A good number of the siblings of his wife, Hannah Marsh, moved to the area as well (her brother Matthias - who also happens to be my 5th g-grandfather - I am a "double Marsh" descendant - her sister, Mary, brother Benjamin, brother Samuel William, sister Charlotte ...).
"Asa was only about three years old when his family moved from Dutchess County to Vermont . . . Asa's parents ran an inn in Manchester, Vermont. Before starting his first trip to Canada in 1791, Asa Weller consulted with his father-in-law, Colonel Marsh, concerning the geography of that portion of the continent . . . Asa was probably accompanied by one of his brothers, Eliakim or Ebenezer . . . They returned to Manchester in the following year.Asa had business to settle and property to sell before emigrating with his family (in 1793). Asa started his boat portaging services shortly after he got settled in Carrying Place.He made it possible to transport bateaux from the Bay of Quinte to Weller's Bay, using his low slung four-wheeled wagon.Oxen were his source of power for the heavy loads."
Excerpt from the Weller Family History by Burton Weller Eagles.