20 世纪40年代，王振铎复原了古文献中提到的天然磁石勺“司南”，但后人始终未能重复实现此方案，其可行性长期受到质疑。本文作者采集到了具有较高天然剩余磁化强度的磁石，与中国古文献记载的磁石磁性相近。仿照古代石器加工技术，将这种磁石切割、打磨成勺状。在加工过程中，磁石勺的退磁可以忽略；加工完成后，外形变化引发内部磁场重新平衡，磁矩略有下降，后又长期保持稳定。实测证明，磁石勺始终具有很好的指向性。古地磁研究显示，中国北方地磁场水平分量在两千多年来呈显著的M形变化，秦汉时期约为现今的2倍。模拟古代地磁场进行实测，磁石勺指向性显著提升。此外，实测显示，磁石水浮、悬吊等多种方式都具有一定的指向性。综合研究表明，在先秦至唐代的磁石资源、地磁场、知识和工艺等条件下，古人有多种方式实现磁性指向，磁石勺是其中的最佳方案。

In the 1940s, Wang Zhenduo 王振铎 re-created the sinan 司南 (southpointing loadstone spoon) mentioned in ancient texts. However, subsequent researchers were unsuccessful in their attempts to replicate this design, resulting in longstanding questions over its feasibility. Loadstones with high natural remanent magnetization acquired today resemble the magnetism of those recorded in premodern Chinese documents. By simulating ancient stoneware processing techniques, a loadstone was cut and polished into a spoon shape. It was found that during the course of processing the loadstone spoon, demagnetization was negligible, while after completion, the internal magnetic field was rebalanced due to the change in shape, and the magnetic moment decreased slightly then stabilized for the long term. Experiments of this sort carried out by the author have testified to the enduring and reliable directivity of the resulting loadstone spoon. Paleo-magnetic research indicates that over the past two millennia the horizontal component of the geomagnetic field intensity in northern China underwent a clear M-shaped development. The level in the Qin and Han dynasties is approximately double that of the current day. Using a simulated ancient geomagnetic field, experiments have revealed that multiple methods, such as the "water floating method" and "hanging method," could manifest a degree of geo-directivity. The comprehensive studies carried out demonstrate that the loadstone spoon is the most optimal among these diverse means for attaining magnetic directivity from the Pre-Qin period (before 221 BCE) to the Tang dynasty (618–907 CE) in view of the availability of loadstone, the state of the geomagnetic field, and existing knowledge and techniques.