Therefore, people of black ancestry with known white lineage became classified as white. This was the opposite of the later "one-drop rule" of hypodescent in the United States, whereby persons of any known African ancestry were classified as black. As white Democrats regained power in state legislatures after the Reconstruction era, they asserted white supremacy, and passed laws for racial segregation and Jim Crow. The one-drop rule was formalized in laws passed in the South in the early 20th century, after the whites had disenfranchised most blacks at the turn of the century by creating barriers to voter registration and voting. During the 19th century, however, many southern states had looser constructions of race; in early 19th-century Virginia, for instance, if a person was seven-eighths white and free, the individual was considered legally white. Children born to slave mothers were considered slaves, no matter what their ancestry, and many were of mixed heritage. Among the most famous were the mixed-race children of Thomas Jefferson by his slave Sally Hemings. He freed all four surviving children when they came of age: two informally, by letting them "walk away," and the two younger sons in his will. Abolitionists During the mid-19th century, a committee of abolitionists was formed in Puerto Rico that included many prominent Puerto Ricans. Dr. Ramón Emeterio Betances (1827–1898), whose mixed-race parents were wealthy landowners, believed in abolitionism, and together with fellow Puerto Rican abolitionist Segundo Ruiz Belvis (1829–1867), founded a clandestine organization called "The Secret Abolitionist Society." The objective of the society was to free slave children by paying for freedom when they were baptized. The event, which was also known as "aguas de libertad" (waters of liberty), was carried out at the Nuestra Señora de la Candelaria Cathedral in Mayagüez. When the child was baptized, Betances would give money to the parents, which they used to buy the child's freedom from the master. José Julián Acosta (1827–1891) was a member of a Puerto Rican commission, which included Ramón Emeterio Betances, Segundo Ruiz Belvis, and Francisco Mariano Quiñones (1830–1908). The commission participated in the "Overseas Information Committee" which met in Madrid, Spain. There, Acosta presented the argument for the abolition of slavery in Puerto Rico. On November 19, 1872, Román Baldorioty de Castro (1822–1889) together with Luis Padial (1832–1879), Julio Vizcarrondo (1830–1889) and the Spanish Minister of Overseas Affairs, Segismundo Moret (1833–1913), presented a proposal for the abolition