But as the Bissextile is necessary to complete the solar course, and as I have not any certain knowledge of the manner in which the Indians effected that addition, I will exhibit the method adopted by the Mexicans, their computation being very analogous to that of Yucatan, which in its origin probably emanated from Mexico.
"Incidents of Travel in Yucatan, Vol. I."
John L. Stephens
In a treatise published by Akerman, the opinion is expressed that the Indians, at the end of their cycle of 52 years, added a week of days in lieu of the Bissextile days which had been neglected.
"Incidents of Travel in Yucatan, Vol. I."
John L. Stephens
Every year that can be divided by four without a remainder is Bissextile or leap year, with the exception that one leap year is cut off in the century.
"Amusements in Mathematics"
Henry Ernest Dudeney