千金云。黄帝曰。灸不三分。是谓徒冤。炷务大也。小弱乃小作之。又曰。小儿七日以
上。
能愈。则是艾炷欲其大。惟头与四肢欲小耳。明堂上经乃曰。艾炷根据小箸头作。其病脉粗细
。状如细线。但令当脉灸之。雀粪大炷亦能愈疾。又有一途。如腹中疝瘕 癖伏梁气等。惟
须大艾炷。故短剧曰。腹背烂烧。四肢则但去风邪而已。不宜大热。如巨阙、鸠尾。灸之不
过四七炷。只根据竹箸头大。但令正当脉灸之。艾炷若大。复灸多。其人永无心力。如头上灸
多。令人失精神。背脚灸多。令人血脉枯竭。四肢细而无力。既失精神。又加细节。令人短
寿。王节斋曰。面上艾炷须小。手足上则可粗。
下经云。古来灸病。忌松、柏、枳、橘、榆、枣、桑、竹八木火。切宜避之。有火珠曜
日。
以艾引之。凡仓卒难备。即不如无木火。清麻油点灯上烧艾茎点灸。兼滋润灸疮。至愈不疼
。用蜡烛更佳。良方云。凡取火者。宜敲石取火。或水精镜于日得太阳火为妙。天阴则以槐
木取火。今行舟人以铁钝刀击石。以纸灰为丸。在下承之。亦得火。
按周礼夏官司 掌行火之政令。四时变国火以救时疾。邹子曰。春取榆柳之火。夏取枣
杏之火
火。只根据取五火而已。秦汉而下。医家不识此意。
《千金方》记载：黄帝说，艾灸时艾炷如果不达到三分厚，就是白白让患者受苦。因此艾炷务必做得大一些；如果患者体质虚弱，则可以稍微做小一点。又说，对于出生七天以上的婴儿，只要艾灸得当就能痊愈，这说明艾炷应该尽量大，只有头部和四肢部位的艾炷应当做小。《明堂上经》却说，艾炷的大小应根据小筷子的头来制作。如果病症的脉象粗细，形状像细线一样，只要让艾炷正对经脉施灸，即使只有麻雀蛋大小的艾炷也能治愈疾病。还有一种情况，比如腹中的疝气、瘕积、癖块、伏梁气等病证，必须使用大的艾炷。所以《短剧》中说，腹部和背部可以烧得焦烂（指深灸），而四肢则只需祛除风邪即可，不宜用太热的灸法。例如巨阙穴、鸠尾穴，艾灸不超过四七二十八壮，只根据竹筷子头的大小来制作艾炷，只要正对经脉施灸即可。如果艾炷过大，且艾灸次数过多，病人会永远感到心力不足。如果在头部艾灸过多，会让人丧失精神；在背部和脚部艾灸过多，会让人血脉枯竭，四肢纤细无力。既丧失了精神，又加重了细节上的损伤，使人寿命缩短。王节斋说，面部的艾炷必须小，手足部位则可以稍粗。
《下经》记载：自古以来艾灸治病，忌讳使用松、柏、枳、橘、榆、枣、桑、竹这八种木材的火。务必避开这些火源。如果有火珠在阳光下聚焦引燃艾草最好。凡是仓促之间难以准备上述材料，还不如不用木柴之火。可以用清麻油点灯，在灯上燃烧艾茎进行点灸，这样既能滋润灸疮，直到愈合也不疼痛，使用蜡烛效果更好。《良方》记载：凡是取火的人，适宜敲石取火，或者用水晶镜对着太阳获取阳光之火为妙。天气阴沉时则用槐木取火。现在行船的人用钝铁刀敲击石头，用纸灰做成丸状垫在下面承接，也能得到火。
按《周礼·夏官》记载：掌管行火的政令，四季变换国家的用火以救治时令疾病。邹子说：春天取榆树、柳树之火，夏天取枣树、杏树之火……只取这五种火而已。秦汉以后，医家不再理解其中的深意。
The *Qianjin Fang* (Thousand Gold Formulas) records: The Yellow Emperor said, "If moxibustion is not three *fen* in thickness, it is a futile injustice." Therefore, the moxa cone must be large; if the patient is weak, it may be made smaller. It is also stated that for infants older than seven days, if treated correctly, they can be cured; this implies that moxa cones should be as large as possible, except for the head and limbs, where they should be small. The *Mingtang Shangjing* (Upper Classic of the Mingtang) states, however, that the size of the moxa cone should correspond to the head of a small chopstick. If the disease pulse is fine and thread-like, as long as the moxa is applied directly on the vessel, even a cone the size of a sparrow's egg can cure the disease. There is another category, such as abdominal hernia (*shan*), masses (*jia*), accumulations (*pi*), and Fu-Liang Qi, which require large moxa cones. Thus, the *Duanju* (Short Treatise) states that the abdomen and back can be burned deeply (scorched), while the limbs only need to dispel wind pathogens and should not undergo excessive heat. For example, at the Juque (CV14) and Jiutui (CV15) acupoints, moxibustion should not exceed 28 cones (four times seven), sized according to the head of a bamboo chopstick, applied directly on the vessel. If the moxa cones are too large and the number of applications is excessive, the person will permanently lack heart and strength. Excessive moxibustion on the head causes loss of spirit; excessive moxibustion on the back and feet causes exhaustion of blood vessels, resulting in thin and weak limbs. Losing one's spirit and adding to these deficits shortens life. Wang Jiezhai said, "Moxa cones on the face must be small, but those on the hands and feet can be coarser."
The *Xiajing* (Lower Classic) records: Since ancient times, in treating diseases with moxibustion, one must avoid the fire from eight types of wood: pine, cypress, zanthoxylum, citrus, elm, jujube, mulberry, and bamboo. One must strictly avoid them. If there is a fire lens (fire pearl) to focus sunlight and ignite the mugwort, that is ideal. In emergencies when these are unavailable, it is better not to use wood fire at all. One can light a lamp with pure hemp oil and burn the stem of the mugwort on the flame for point moxibustion; this also moistens the moxa sore, ensuring it heals without pain. Using candles is even better. The *Liangfang* (Good Prescriptions) records: When obtaining fire, it is appropriate to strike flint to create sparks, or to use a crystal mirror to catch solar fire under the sun, which is excellent. On cloudy days, locust wood (*huai mu*) is used to obtain fire. Nowadays, boatmen use a dull iron knife to strike stones, placing paper ash pills underneath to catch the spark, which also yields fire.
According to the *Rites of Zhou* (Zhou Li), Chapter Xia Guan (Summer Officials): "Those in charge of fire administration issue orders to change national fires according to the four seasons to save people from seasonal illnesses." Zou Yan said: "In spring, take fire from elm and willow; in summer, take fire from jujube and apricot..." Only these five fires are taken. From the Qin and Han dynasties onward, medical practitioners no longer understood this meaning.