They are therefore understood as being alive. Many of the stones will have been collected from the landscape and then divination used to determine which ones contain an oricha and, if so, which oricha it is. Specific "otanes" sometimes display traits linking them to particular oricha; for example ocean stones are linked with Yemaya, river pebbles with Oshun, and meteorite fragments with Chango. Each oricha is deemed to prefer a particular color and number of "otanes" in "sopera" devoted to them; Chango has six or ten black stones, Obatala has eight white stones, while Ochun favors five yellow stones, for instance. Many practitioners place great emphasis on the stones, perceived as being sources of power, something linked to "aché". Adherents believe that older stones have more "aché" than younger ones. Some of the most powerful stones are claimed to have been brought to Cuba from Africa by enslaved persons who concealed them within their stomachs during the crossing of the Atlantic Ocean. The "otanes" undergo a "bautismo" (baptism) rite; this allows them to be "born" and involves the being washed in "osain", a mixture of herbs and water, after which they are "fed" with animal blood. When a santero or santera receives their stones, they take an oath to protect them at all times and to feed them at least annually. By feeding them, initiates believe that the stones gain the strength to aid people. Also placed within the "sopera", alongside the "otanes", are a series of cowrie shells; usually 18 are added although the precise number differs depending on which oricha the "sopera" is devoted to. In addition to their altar to the oricha, many practitioners also have altars set aside for the spirits of the dead. Such altars typically consist of a white-covered table known as a "bóveda", something derived from the White Table of Kardecian Spiritism. These often contain photographs of deceased relatives as well as offerings placed to them. Popular offerings for the spirits of the dead include seven glasses of water, a "Cafecito" coffee, and the "aguardiente" liquor. Many practitioners will also enshrine their family ancestors on the floor of the bathroom, under the sink. This location is chosen so that the ancestors are located below the vertical water pipes, allowing the spirits to transition between the realms via water, which is their preferred medium for travel.