مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٢٣٣ - SAJDATAYN(TWO PROSTRATIONS)

a sign for prostration with his head while he is standing and should recitetashahhud in the standing posture and his prayers will be in order.
١٠٨٤. The recommended precaution is that in the first unit and in the third unit which does not contain tashahhud (like the third unit in midday, afternoon andnight prayers) one should sit still for a while after the second prostration and then stand up.
 THINGS ON WHICH PROSTRATION IS IN ORDER
THINGS ON WHICH PROSTRATION IS IN ORDER
١٠٨٥. Prostration should be performed on earth and on those things which are not edible and which grow from earth (e.g. wood and leaves of trees). It is not inorder to perform prostration on things which are used as food or dress (e.g. wheat, barley and cotton etc.) or on things which are not considered to be parts of the earth(e.g. gold, silver, agate, tar etc.).
١٠٨٦. The obligatory precaution is that prostration should not be performed on the leaves of vine before they become dry.
١٠٨٧. It is in order to perform prostration on those things which grow from earth and serve as food for animals (for example grass, hay etc.).
١٠٨٨. It is in order to perform prostration on flowers which are not edible and also on medicinal herbs which grow from earth (for example on the flowers likeviolet or borage etc.).
١٠٨٩. Performing prostration on a grass which is usually eaten in some cities, but is not usually eaten in other cities, and on unripe fruit is not in order.
١٠٩٠. It is in order to perform prostration on lime-stone and gypsum and the recommended precaution is that prostration should not be optionally performed on bakedgypsum, lime, brick and baked earthenware and other things resembling them.
١٠٩١. It is in order to perform prostration on paper even if it is