Attar, also known as ittar, is an essential oil derived from botanical or other natural sources. Most commonly these oils are extracted via hydrodistillation or steam distillation. The Persian physician Ibn Sina was the first to derive the attar of flowers from distillation. Attar can also be expressed by chemical means but generally natural perfumes which qualify as attars are distilled with water. The oils are generally distilled into a wood base such as sandalwood and then aged. The aging period can last from one to ten years depending on the botanicals used and the results desired. Technically attars are distillates of flowers, herbs, spices and other natural materials such as baked soil over sandalwood oil/liquid paraffins using hydrodistillation technique involving a still and receiving vessel. These techniques are still in use at Kannauj in India.