Muhammed ibn Umail al-Tamimi
Ibn Umayl, Muhammed ibn Umail at-Tamîmî (Arabic: أبو عبد الله محمد بن أميل التميمي ) was an alchemist of the tenth century. He can be dated to 900–960 AD (286-348 AH) on the basis of the names of acquaintances he mentioned. Whether or not Ibn Umayl was born in Egypt his writings indicate he mainly lived and worked there, with connections to North Africa and possibly Andalusia.
There is an allusion to him in Chaucer's Canon's Yeoman's Tale (the "book senior"); the tale itself having alchemy as a theme. Chaucer’s source is said to be the Chimica senioris zadith tabula; Chaucer believed it written by a follower of Plato.
Attributed to ibn Umail are the Hall ar-Rumuz (Explanation of the symbols), the Kitâb mafâtîh al-hikma al-`uzmâ, and the Kitâb al-mâ' al-waraqî wa al-ardh al-najmîya, a commentary on the alchemical poem Risâla al-shams ilâ al-hilâl (in Latin, Epistola solis ad lunam crescentem, the letter of the Sun to the waxing Moon).
Allegorical Alchemy 
Ib Umayl was what is now called an allegorical alchemist. He saw himself as following his “predecessors among the sages of Islam” in rejecting alchemists who take their subject literally. Although such discovered by experiment the sciences of metallurgy and chemistry, Ibn Umayl felt the allegorical meaning of alchemy is the precious goal that is tragically overlooked. He wrote:
“Eggs are only used as an analogy... the philosophers … wrote many books on such things as eggs, hair, the biles, milk, semen, claws, salt, sulphur, iron, copper, silver, mercury, gold and all the various animals and plants … But then people would copy and circulate these books according to the apparent meaning of these things, and waste their possessions and ruin their souls” The Pure Pearl chap. 1 (4.4)
"... none of those people who are famous for their wisdom could explain a word of what the philosophers said. In their books they only continue using the same terms that we find in the sages .... What is necessary, if I am a sage to whom secrets have been revealed, and if I have learned the symbolic meanings, is that I explain the mysteries of the sages."  (p.43. I. 17-21)
- Starr, Peter: Towards a Context for Ibn Umayl ..., Çankaya University, Balgat, Ankara, Turkey. 2010
- Or Senior Zadith (sometimes just Senior), derived from the honorific al-sadik, becoming Zadith phonetically, and the title Sheikh becoming 'senior' by translation into Latin; this explanation is from Julius Ruska, Senior Zadith = Ibn Umail. Orientalistische Literaturzeitung 31, 1928, pp. 665-666.
- From an erroneous translation of ibn Umail. So also Zadith ben Hamuel.
- Also known as Senioris Zadith filii Hamuelis tabula chymica, the chemical tables of Senior Zadith son of Hamuel. It was published in the 1660 Theatrum chemicum, as Senioris antiquissimi philosophi libellus.
- Title page of 1605 edition, as part I of Philosophiae Chymicae IV. Vetvstissima Scripta
- Julius Ruska, Studien zu Muhammad Ibn Umail al-Tamimi's Kitab al-Ma' al-Waraqi wa'l-Ard an-Najmiyah,Isis, Vol. 24, No. 2 (Feb., 1936), pp. 310-342.
- Another (doubtful) attribution is the illustrated Aurora consurgens, which in its text quotes Senior, perhaps c.1400; this is also said to be by Thomas Aquinas.
- Stapleton H.E, and Husein M.H. Three Arabic treatises on alchemy by Muhammad ibn Umail (10th century AD) Asiatic Society of Bengal, Calcutta, 1933, 12.1 p. 1–213. Stapleton/Husein's seminal work was reprinted in facsimile in 2002 as Ibn Umayl (fl. c. 912). Texts and Studies (Collection "Natural Science in Islam", vols. nº 55-75). Ed. F. Sezgin. ISBN 3-8298-7081-7. Published by Institut für Geschichte der Arabisch-Islamischen Wissenschaften, University of Frankfurt, Westendstrasse 89 , D-60325 Frankfurt am Main.