The estimate of Martha’s birthdate is very rough, as her age in the censuses varies considerably.

The earliest record is the 1850 census, which lists her as age 33, implying a birthdate around 1817. The next two censuses, though, list her as age 40 in 1860 and 50 in 1870, implying a birthdate around 1820. The 1880 census lists her as age 68, implying a birthdate around 1812, which is unlikely since her youngest son Eli was born in 1862.

Generally ages reported earlier in life are more accurate, but a birth in 1817 would conflict with the birth of her brother Joseph, documented as 21 Jan 1817, and even a birth in 1816 would be tight. So she was most likely born either in 1815, or in 1818 to 1819.

Martha's will, dated 1887 and probated 1890 in Floyd Co., VA, names sons Eli Wade & Harvey Wade, daughters Miriam W. Dickerson, Mary J. Quessenberry, and Eliza A. Simmons, and granddaughter Martha R. L. Jennings.

1850 census of Floyd Co., Va, enumerated 3 Sep, lists on p. 440 as family #868:
Isaac Wade, 37; Martha, 33; Harvey, 10; Myram, 8; Mary, 6; Eliza, 4; Joshua, 2. All born Floyd Co.

1860 census of Floyd Co., Virginia, Indian Valley district, enumerated 9 Aug, lists on pp. 148-149 as family #1077/1004:
Isaac Wade, 47, farmer; Martha, 40; Harvey, 20; Miriam, 17; Mary, 16; Elizabeth, 13; Joshua, 11; Eliza, 6; Hannah, 3; Celia, 8; Anna, 4/12. All born Va/Va/Va.

1870 census of Floyd Co, Virginia, Jacksonville township, enumerated 18 June, lists on p 5 as family #31/30:
Wade, Isaac, 56, farming; Martha, 50; Emma Rosabel, 10; Eli, 5; Quesenberry, Leroy, 5, adopted; Dehart, Mack, 21 (black), farm laborer. (I do not know the parents of Leroy Quesenberry.)

1880 census of Floyd Co., Virginia, Jacksonville district, enumerated 25 June, lists on p. 43 as family #411:
Isaac Wade, 67, farmer; Martha, 68; Eli, 15. All born Va Va Va, relationships blank for Martha and Eli. Quesenberry, Leroy, 15, servant, b. Va Va Va.

Ther preceding household is headed by his brother John Wade, age 68.